In-situ deposition of film stacks

ABSTRACT

An apparatus for depositing film stacks in-situ (i.e., without a vacuum break or air exposure) are described. In one example, a plasma-enhanced chemical vapor deposition apparatus configured to deposit a plurality of film layers on a substrate without exposing the substrate to a vacuum break between film deposition phases, is provided. The apparatus includes a process chamber, a plasma source and a controller configured to control the plasma source to generate reactant radicals using a particular reactant gas mixture during the particular deposition phase, and sustain the plasma during a transition from the particular reactant gas mixture supplied during the particular deposition phase to a different reactant gas mixture supplied during a different deposition phase.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional claiming priority to U.S. applicationSer. No. 12/970,846, titled “IN-SITU DEPOSITION OF FILM STACKS” andfiled on Dec. 16, 2010, which claims priority to U.S. Provisional PatentApplication Ser. No. 61/317,656, titled “IN-SITU PLASMA-ENHANCEDCHEMICAL VAPOR DEPOSITION OF FILM STACKS,” and filed on Mar. 25, 2010;U.S. Provisional Patent Application Ser. No. 61/382,465, titled “IN-SITUPLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION OF FILM STACKS,” and filed onSep. 13, 2010; U.S. Provisional Patent Application Ser. No. 61/382,468,titled “SMOOTH SILANE-BASED FILMS,” and filed on Sep. 13, 2010; and U.S.Provisional Patent Application Ser. No. 61/394,707, titled “IN-SITUPLASMA-ENHANCED CHEMICAL VAPOR DEPOSITION OF FILM STACKS,” and filed onOct. 19, 2010, the entirety of which are hereby incorporated herein byreference for all purposes.

BACKGROUND

Various thin film layers for semiconductor devices may be deposited bychemical vapor deposition (CVD) and/or plasma-enhanced chemical vapordeposition (PECVD) processes. Some deposition processes generate smallgas phase particles during process, which may decorate a depositionsurface, potentially contaminating the device. Such particles may clingto the device, potentially blocking subsequent etch and/or depositionevents, which may ultimately lead to device failure. Further, particlesmay be knocked off the device downstream, potentially contaminatingother process tools.

Some approaches to addressing gas-phase particle generation may attemptto suppress particle generation by diluting reaction conditions.However, such approaches may diminish film deposition rates, requiringthe installation and maintenance of additional process tools to supporta production line. Further, films produced by such approaches may havephysical or electrical characteristics that provide inadequate deviceperformance. Further still, such approaches may not address particlesformed in various exhaust hardware for the process tool, which mayback-stream and contaminate the device. These particles may be deliveredto the substrate surface during deposition. Once coated by additionalfilm material, the small size of the particles may be magnified, causingripples and distortions at the film surface. These ripples may make itdifficult to pattern the resulting films.

Patterning problems may also be caused by rough films. Some traditionalatomic layer deposition (ALD), chemical vapor deposition (CVD),high-density plasma chemical vapor deposition (HDP-CVD) andplasma-enhanced chemical vapor deposition (PECVD) processes fordepositing film layers may produce unacceptably rough films, causeunacceptable interfacial mixing between film layers, and may haveinterfacial defects caused by vacuum breaks between successivelydeposited film layers. The resulting rough film interfaces andinterfacial defects may be magnified by subsequently deposited layers asthe film stack is built, so that the top surface of the film stack maybe unacceptably rough for downstream patterning processes. Further,interfacial defects within the film stack may lead to structural and/orelectrical defects in the resulting integrated device.

SUMMARY

Various embodiments are described herein related to depositing filmstacks in a process tool in-situ (i.e., without a vacuum break or airexposure) using plasma-enhanced chemical vapor deposition (PECVD). Inone example, a method for depositing, on a substrate, a film stackincluding films of different compositions in-situ in a process stationusing a plasma is described. The method includes, in a firstplasma-activated film deposition phase, depositing a first layer of filmhaving a first film composition on the substrate; in a secondplasma-activated deposition phase, depositing a second layer of filmhaving a second film composition on the first layer of film; andsustaining the plasma while transitioning a composition of the plasmafrom a first plasma composition of the first plasma-activated filmdeposition phase to a second plasma composition of the secondplasma-activated film deposition phase.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to implementations that solveany or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example embodiment of a film stackincluding alternating layers of a first film and a second film depositedon a substrate.

FIG. 2 shows an atomic force microscopy (AFM) image of a surface of anexample tetraethyl orthosilicate (TEOS)-based plasma-enhanced chemicalvapor deposition (PECVD) SiO₂ film deposited at the top of a film stackincluding 11 pairs of alternating SiN/SiO₂ layers.

FIG. 3 shows an atomic force microscopy (AFM) image of a surface of anexample conventional silane-based PECVD SiO₂ film deposited at the topof a film stack including 11 pairs of alternating SiN/SiO₂ layers.

FIG. 4 shows an atomic force microscopy (AFM) image of a surface of anexample ultra-smooth PECVD SiO₂ film deposited according to anembodiment of the present disclosure at the top of a film stackincluding 14 pairs of alternating SiN/SiO₂ layers.

FIG. 5 graphically shows a comparison of absolute roughness betweenconventional PECVD and atomic layer deposition (ALD) SiO₂ films andexample ultra-smooth PECVD SiO₂ films deposited according to embodimentsof the present disclosure.

FIG. 6 schematically shows an embodiment of a film stack includingexample ultra-smooth PECVD SiO₂ films deposited according to anembodiment of the present disclosure, the ultra-smooth PECVD SiO₂ filmsinterleaved with silicon nitride films.

FIG. 7 schematically shows an ultra-smooth PECVD SiO₂ film depositedaccording to an embodiment of the present disclosure deposited on top ofthe film stack schematically depicted in FIG. 6.

FIG. 8 shows an AFM image of a silicon nitride surface exposed at thetop of the film stack schematically depicted in FIG. 6.

FIG. 9 shows an AFM image of a surface of a 300 Å-ultra-smooth PECVDSiO₂ film deposited according to an embodiment of the present disclosureat the top of the film stack schematically depicted in FIG. 7.

FIG. 10 shows an AFM image of a surface of a 3000 Å-ultra-smooth PECVDSiO₂ film deposited according to an embodiment of the present disclosureat the top of the film stack schematically depicted in FIG. 7.

FIG. 11 schematically shows another embodiment of a film stack includingexample ultra-smooth PECVD SiO₂ films deposited according to anembodiment of the present disclosure, the ultra-smooth PECVD SiO₂ filmsinterleaved with silicon nitride films.

FIG. 12 graphically shows an example relationship between the thicknessof ultra-smooth PECVD SiO₂ films deposited according to an embodiment ofthe present disclosure, conventional TEOS-based PECVD SiO₂ films, andconventional silane-based PECVD SiO₂ films and absolute roughnessmeasurements for those films.

FIG. 13 schematically shows a silicon nitride film deposited on top ofthe film stack schematically depicted in FIG. 11.

FIG. 14 graphically shows an example relationship between the thicknessof ultra-smooth PECVD SiO₂ films deposited according to an embodiment ofthe present disclosure, conventional TEOS-based PECVD SiO₂ films, andconventional silane-based PECVD SiO₂ films and absolute roughnessmeasurements for an 800 Å-silicon nitride film deposited on each ofthose SiO₂ films.

FIG. 15 shows a flow chart illustrating a method of depositing anultra-smooth PECVD silicon-containing film according to an embodiment ofthe present disclosure.

FIG. 16 graphically shows an example relationship between surfaceroughness and silane flow rate for conventional PECVD SiO₂ films andultra-smooth PECVD SiO₂ films deposited according to embodiments of thepresent disclosure.

FIG. 17 graphically shows an example relationship between silane flowrate and SiO₂ film deposition rate for the example films shown in FIG.7.

FIG. 18 graphically shows relationships between process station pressureand SiO₂ film deposition rates for ultra-smooth PECVD SiO₂ filmsdeposited according to embodiments of the present disclosure, the SiO₂films being deposited from ultra-smooth PECVD processes having similarsilane flow rates but different total gas flow rates.

FIG. 19 graphically shows a relationship between film stress, SiO₂ filmdeposition rate, and silane flow rate for ultra-smooth PECVD SiO₂ filmsdeposited according to embodiments of the present disclosure.

FIG. 20 graphically shows relationships between film stress, substratebow, and film thickness for an ultra-smooth PECVD SiO₂ film depositedaccording to an embodiment of the present disclosure.

FIG. 21 graphically shows a comparison of Fourier transform infraredspectra showing Si—O bond-stretching mode data for a thermally-grownSiO₂ film, a TEOS-based PECVD SiO₂ film, and an ultra-smooth PECVD SiO₂film deposited according to an embodiment of the present disclosure.

FIG. 22 graphically shows a relationship between absolute roughness ofultra-smooth PECVD SiO₂ films deposited according to embodiments of thepresent disclosure and the power level of a high-frequency plasma.

FIG. 23 graphically illustrates the dependence of process stationpressure for ultra-smooth PECVD SiO₂ films deposited according toembodiments of the present disclosure and absolute roughness.

FIG. 24 graphically shows a relationship between within-substrate rangenon-uniformity and process station pressure for ultra-smooth PECVD SiO₂films deposited according to embodiments of the present disclosure.

FIG. 25 graphically shows a relationship between deposition rate forultra-smooth PECVD SiO₂ films deposited according to embodiments of thepresent disclosure and an argon flow rate.

FIG. 26 graphically shows a relationship between absolute roughness ofultra-smooth PECVD SiO₂ films deposited according to embodiments of thepresent disclosure and an argon flow rate.

FIG. 27 graphically shows another comparison of Fourier transforminfrared spectra showing Si—O bond-stretching mode data for exampleultra-smooth PECVD silicon oxide and silicon oxynitride films depositedaccording embodiments of the present disclosure.

FIG. 28 graphically shows a comparison of Fourier transform infraredspectra showing Si—N bond-stretching mode data for an exampleconventional silicon nitride film and for example ultra-smooth PECVDsilicon nitride films deposited according embodiments of the presentdisclosure.

FIG. 29 graphically shows another comparison of Fourier transforminfrared spectra showing N—H bond-stretching mode data for an exampleconventional silicon nitride film and for example ultra-smooth PECVDsilicon nitride films deposited according embodiments of the presentdisclosure.

FIG. 30 graphically shows another comparison of Fourier transforminfrared spectra showing Si—H bond-stretching mode data for an exampleconventional silicon nitride film and for example ultra-smooth PECVDsilicon nitride films deposited according embodiments of the presentdisclosure.

FIG. 31 shows a flow chart illustrating a method of depositing a filmstack in-situ using a plurality of plasma-activated film depositionphases according to an embodiment of the present disclosure.

FIG. 32 schematically shows a timing diagram for an example PECVDprocess according to an embodiment of the present disclosure.

FIG. 33 schematically shows another timing diagram for an example PECVDprocess according to an embodiment of the present disclosure.

FIG. 34 shows a flow chart illustrating a method of transitioning,in-situ, from a first film deposition process to a second filmdeposition process with an intervening purge step according to anembodiment of the present disclosure.

FIG. 35A shows a flow chart illustrating a first portion of a method ofpurging one or more portions of a reactant delivery line shared by aprocess reactant of the first film deposition phase that is incompatiblewith a process reactant of a second film deposition phase according toan embodiment of the present disclosure.

FIG. 35B shows a flow chart illustrating a second portion of the methodof purging one or more portions of a reactant delivery line shared by aprocess reactant of the first film deposition phase that is incompatiblewith a process reactant of a second film deposition phase illustrated inFIG. 35A.

FIG. 36 schematically shows an example PECVD process station accordingto an embodiment of the present disclosure.

FIG. 37 schematically shows an example dual-plenum showerhead accordingto an embodiment of the present disclosure.

FIG. 38 schematically shows an example of a multi-station process toolaccording to an embodiment of the present disclosure.

FIG. 39 schematically shows another example of a multi-station processtool according to an embodiment of the present disclosure.

FIG. 40 schematically shows another example of a multi-station processtool according to an embodiment of the present disclosure.

FIG. 41 schematically shows another example of a multi-station processtool according to an embodiment of the present disclosure.

FIG. 42 schematically shows another example of a multi-station processtool according to an embodiment of the present disclosure.

FIG. 43 schematically shows another example of a multi-station processtool according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Some memory devices, such as NAND flash memory, are arranged intwo-dimensional arrays. Because such memory devices are limited to aplanar arrangement, die size and memory density parameters may constrainthe total memory capacity of the device. In turn, moving to larger diesizes to expand memory capacity may comparatively increase the cost ofthe memory device, which may delay adoption of larger capacity memorydevices. Recently, some approaches for arranging memory gates intothree-dimensional (3D) arrays have been proposed. Some of theseapproaches incorporate of transistors formed by patterning stacks ofalternating film composition. FIG. 1 schematically shows an example filmstack 100 including alternating layers of first film 102 and second film104 on a substrate 106.

Patterning such film stacks can be difficult. For example, rough filmsurfaces caused during deposition and/or film cracks caused by vacuumbreaks between deposition events may cause ripples in subsequentlydeposited layers. Further, ripples and surface irregularities can alsobe caused by particles included in the film as the film is beingdeposited. Such small particle defects may be generated from theinteraction of incompatible processes gases during deposition, during anin-situ transition from one film deposition process to another, and/orduring wafer handling operations in ex-situ deposition processes. As thefilm stack is built, these roughness- and defect-caused undulations maygrow in size and may cause focus, exposure, and etch problems indownstream patterning operations. Thus, it is desirable for each layerto be highly smooth.

Accordingly, various embodiments are disclosed herein that are relatedto providing smooth film surfaces. For example, embodiments aredescribed below related to ultra-smooth film deposition chemistries andprocesses, which may result in ultra-smooth film surfaces. Further,embodiments are also described below related to low defect tool hardwareand processes for depositing film stacks without intervening vacuumbreaks, which may also result in ultra-smooth film stack surfaces.

While many plasma-enhanced chemical vapor deposition (PECVD) or chemicalvapor deposition (CVD) processes may be used to deposit such thin films,building thick stacks of multiple layers may present manufacturingchallenges. Some approaches for depositing such silicon dioxide filmsinclude using tetraethyl orthosilicate (Si(OC₂H₅)₄, or TEOS)-basedplasma-enhanced chemical vapor deposition (PECVD) processes orsilane-based PECVD processes. However, these conventional PECVDprocesses may produce unacceptably rough films. For example, aconventional silane-based PECVD process for depositing SiO₂ exhibits anabsolute roughness (Ra) of 7.2 Å for a 1000 Å film deposited on a baresilicon substrate while a conventional TEOS-based PECVD process fordepositing SiO₂ exhibits an roughness of 4.5 Å Ra for a 1000 Å filmdeposited on a bare silicon substrate.

The effect of stacking rough films can be cumulative, so that a topsurface of the film stack may be rougher than the individual films.FIGS. 2 and 3 show surface roughness images for example SiN/SiO₂ filmstacks measured by atomic force microscopy (AFM). FIG. 2 depicts an AFMimage 200 of a film stack having 11 pairs of SiN/SiO₂ films using aTEOS-based PECVD SiO₂ deposition process. For reference, the roughnessof a 1000 Å silicon nitride film deposited on a bare silicon substrateis 5.1 Å Ra.

In the example shown in FIG. 2, the TEOS-based SiO₂ film at the top ofthe film stack exhibits a roughness of approximately 9.9-10.6 Å Ra. FIG.3 depicts an AFM image 300 of a film stack having 11 alternating pairsof SiN/SiO₂ films using a silane-based PECVD SiO₂ process (e.g., usingsilane at a flow rate of approximately 500-600 sccm). In the exampleshown in FIG. 3, the SiO₂ film has a roughness of approximately 17 to 19Å Ra. Thus, it will be appreciated that the conventional PECVD SiO₂processes may deposit films that are comparatively rougher than theunderlying film.

Some other approaches for depositing smooth silicon dioxide films employhigh-density plasma chemical vapor deposition (HDP-CVD) processes.However, HDP-CVD processes typically employ ion densities of greaterthan 2×10¹⁰ ions/cm³. Such high ion density deposition environments mayunselectively sputter underlying films as the SiO₂ layer is deposited.This may lead to unacceptable interlayer oxidation, potentially leadingto electrical defects or structural defects at the film interfaces.Further, HDP-CVD processes typically use inductively-coupled plasmasources, which are comparatively more expensive and are comparativelymore likely to generate defects during process relative to thecapacitively-coupled plasma sources used in PECVD processes.

Further, because HDP-CVD process equipment may not be suitable fordepositing more than one film composition in-situ, vacuum breaks may berequired during processing, potentially leading to the inclusion ofinterlayer defects. For example, in one scenario, film cracking mayresult from vacuum break conditions as substrates are exchanged betweenseparate tools. In another scenario, a film may absorb atmosphericmoisture during a vacuum break. Building film stacks using ex-situprocesses may also lead to additional processing equipment expense,because film-specific tools may be required and because added substratehandling times between film-specific tools may reduce fab throughput.

Thus, various embodiments are disclosed herein that are related toplasma-enhanced chemical vapor deposition (PECVD) processes andequipment used for depositing film stacks in-situ without interveningvacuum breaks. Further, various embodiments are described here fordepositing ultra-smooth silicon-containing films, including dielectricfilms such as silicon oxides (e.g., SiO₂ and sub-oxides thereof),silicon oxynitrides, and silicon nitrides, and conductive films such aspolycrystalline and amorphous silicon. Example film stacks that may beconstructed in-situ using the embodiments described herein include, butare not limited to, alternating layers of silicon dioxide and siliconnitride, alternating layers of polycrystalline silicon and silicondioxide, alternating layers of polycrystalline silicon and siliconnitride, and alternating layers of doped and undoped amorphous and/orpolycrystalline silicon, which in some embodiments, may deposited insitu. Further still, various embodiments are described relating to novelin-situ PECVD processes and equipment that may comparatively reducedefect generation relative to conventional PECVD processes and equipmentwhen depositing layers and film stacks such as the examples listedabove.

As an example, FIG. 4 shows an AFM image 400 of an example film stackhaving 14 alternating pairs of a silicon nitride film and anultra-smooth silicon dioxide film deposited according to an example ofan ultra-smooth PECVD process of the present disclosure. In the exampleshown in FIG. 4, the ultra-smooth PECVD SiO₂ top layer has a roughnessof approximately 4.6 Å Ra, exhibiting a greater than two-foldimprovement in surface roughness compared to the conventional PECVD SiO₂processes described above and shown in FIGS. 2 and 3, though someultra-smooth PECVD silicon dioxide films (discussed in more detailbelow) deposited on silicon nitride surfaces exhibit roughness values ofapproximately 3.6 Å Ra. Further, as explained above, the roughness of a1000 Å silicon nitride film deposited on a bare silicon substrate is 5.1Å Ra. Thus, it will be appreciated that, in some embodiments, theultra-smooth PECVD SiO₂ process may provide a top surface roughness thatis less than a roughness of an underlying film. For example, in someembodiments, an ultra-smooth PECVD SiO₂ film may have an absoluteroughness that is approximately 90% or less than the roughness of anunderlying film.

Without wishing to be bound by theory, it is believed that, in someembodiments, the ultra-smooth character of ultra-smooth PECVD films mayresult from conditions where surface adsorption, rearrangement and/orassembly reactions occur at a substantially faster rate and/or ingreater abundance than gas-phase polymerization and adsorptionreactions. Under such conditions, the radicals generated in the plasmamay be relatively more likely to be adsorbed to the substrate and linkon the substrate surface than they are to react in the gas phase abovethe substrate.

Thus, an ultra-smooth PECVD process according to the present disclosuremay provide a film that has an absolute roughness that is substantiallyindependent of film thickness. For example, in some examples, anultra-smooth PECVD SiO₂ film may exhibit a surface roughness of lessthan or equal to 4.5 Å for film thicknesses of up to 3000 Å as measuredon a silicon substrate. For example, FIG. 5 shows a graph 500 comparingsurface absolute roughness as a function of film thickness for silicondioxide films deposited on bare silicon substrates by various exampleprocesses, including a conventional silane-based PECVD process example(points 502), a conventional TEOS-based PECVD process example (points504), and an example ultra-smooth silicon dioxide film deposited by anexample ultra-smooth PECVD process according to the present disclosure(points 506). The example films made by conventional PECVD processesshown in FIG. 5 may be characterized as having gas-phase polymerizationreactions that occur at a faster rate than surface assembly andrearrangement reactions. Thus, points 502 and points 504 trend towardincreasing absolute roughness with increasing film thickness. Incontrast, the example ultra-smooth PECVD silicon dioxide film shown inFIG. 5 exhibits a surface roughness of approximately 2.5 Å Ra for filmthicknesses of up to 3000 Å while having a substantially constantabsolute roughness.

FIG. 5 also shows a comparison between example silicon dioxide filmsdeposited by high-density plasma chemical vapor deposition (HDP-CVD)processes and the ultra-smooth PECVD-deposited silicon dioxide filmexample discussed above. As shown in FIG. 5, the example ultra-smoothPECVD silicon dioxide film has approximately the same absolute surfaceroughness as the example HDP-CVD silicon dioxide film (points 508).However, as explained above, HDP-CVD processes may damage underlyingfilms and may be unable to produce film stacks in-situ. In contrast, asexplained in detail below, ultra-smooth PECVD films may be depositedwithout using high ion densities (e.g., with ion densities of less than2×10¹⁰ ions/cm³) and therefore may maintain a comparatively sharpinterfacial composition boundary with an underlying film. Further,ultra-smooth PECVD films may be deposited in-situ with other filmprocesses, potentially avoiding vacuum breaks when building a filmstack.

FIG. 5 also shows a comparison between an example SiO₂ film deposited byan atomic layer deposition (ALD) process (points 510) and theultra-smooth PECVD film example described above. Like the conventionalPECVD processes, the example film deposited by the ALD process exhibitsa thickness-dependent increase in absolute roughness. While ALDprocesses theoretically deposit a monolayer of film at a time,differences in adsorption of the otherwise segregated depositionprecursors may lead to the formation of condensed phase precursordomains (e.g., the surface may include both chemisorbed and physisorbedprecursor). Such domains may lead to the creation of non-stoichiometricregions of the film, which may cause lattice defects and surfaceroughness in the film. Subsequently-deposited layers may magnify theeffect of the surface roughness. Moreover, the layer-by-layer depositionprocess used in ALD may be comparatively more expensive than a PECVDprocess, both in throughput costs and in equipment costs.

In contrast, and without wishing to be bound by theory, thecomparatively lower surface energies of flatter surfaces (e.g., surfacesapproaching the native roughness of a thermodynamically stableterminated surface) may provide a driving force that allows, via surfacerearrangement and assembly reactions, self-planarization of thedeposited film. Thus, in some embodiments, an ultra-smooth PECVD filmthat is deposited on a comparatively rougher film may still exhibitultra-smooth characteristics. This may provide a highly smooth surfacefor a film stack, even if the film stack comprises comparatively rougherunderlying films.

For example, FIG. 6 schematically shows an embodiment of a film stack600 including example ultra-smooth PECVD SiO₂ films having a depositionrate of approximately 2.3 Å/sec. The example shown in FIG. 6 includes aplurality of 300 Å ultra-smooth PECVD SiO₂ films 604 interleaved with aplurality of 800 Å silicon nitride films 602 and a plurality of 1000 Åultra-smooth PECVD SiO₂ films 606. A final 800 Å silicon nitride film(layer 602A) having a top surface 610 is deposited on top of film stack600. FIG. 7 schematically shows a top layer of ultra-smooth PECVD SiO₂film (layer 702) deposited on top of film stack 600.

FIG. 8 shows an AFM image 800 of silicon nitride surface 610 exposed atthe top of film stack 600 schematically depicted in FIG. 6. As measuredby AFM, silicon nitride surface 610 exhibits an absolute roughness ofapproximately 6.9 Å. For comparative purposes, an 800 Å silicon nitridefilm deposited on a film stack having an identical number of alternatinglayers of silicon dioxide and silicon nitride in which conventionalTEOS-based PECVD SiO₂ films are substituted for ultra-smooth PECVD SiO₂films has an absolute roughness of approximately 10 Å. Thus, theultra-smooth PECVD SiO₂ film yields a comparatively smoother surface atthe top of an overlying silicon nitride relative to a TEOS-based PECVDSiO₂ film.

Subsequent deposition of ultra-smooth PECVD SiO₂ film layer on top ofthe silicon nitride layer may provide additional improvement in topsurface roughness relative to the silicon nitride layer roughness. Forexample, FIGS. 9 and 10 show AFM images 900 and 1000, respectively, oftop surface 710 of ultra-smooth PECVD SiO₂ film layer 702 schematicallydepicted in FIG. 7. As measured by AFM, ultra-smooth PECVD SiO₂ topsurface 710 has an absolute roughness of approximately 5.4 Å when layer702 is deposited at a 300 Å thickness (as shown in FIG. 9), having aroughness approximately 80% of that exhibited by the underlying siliconnitride film. Further, comparatively thicker layers of ultra-smoothPECVD SiO₂ films may provide comparatively smoother top surfaces. Forexample, when layer 702 is deposited at a 3000 Å thickness (as shown inFIG. 10), it exhibits an absolute roughness of approximately 3.6 Å,having a roughness approximately 50% of that exhibited by the underlyingsilicon nitride film. In contrast, when conventional TEOS-based PECVDSiO₂ films are substituted for ultra-smooth PECVD SiO₂ films, there isno reduction in the surface roughness compared that exhibited by thesilicon nitride film. Specifically, each of a 300 Å-thick and a 3000Å-thick TEOS-based PECVD SiO₂ film exhibits an absolute roughness ofapproximately 10 Å.

As described above, in some embodiments, ultra-smooth PECVD films mayexhibit a decreasing surface roughness as the thickness of theultra-smooth PECVD film increases. FIGS. 11 and 12 illustrate anotherexample of such an embodiment. FIG. 11 schematically shows an example ofa film stack 1100 including a 1000 Å-thick conventional silane-basedPECVD SiO₂ film layer 1102 deposited on substrate 106. An 800 Å-thicksilicon nitride layer 1104 is deposited on top of layer 1102. Forreference, the roughness of layer 1104 is approximately 16.3 Å Ra. FIG.11 also shows a top surface 1108 of an example ultra-smooth PECVD SiO₂film layer 1106, layer 1106 being deposited on top of layer 1104. FIG.12 shows a graph 1200 illustrating an example relationship 1202 betweenthe thickness of layer 1106 and the roughness of surface 1108 for anexample ultra-smooth PECVD SiO₂ film deposited at approximately 2.3Å/sec. As shown in FIG. 12, the ultra-smooth PECVD SiO₂ film exhibits aninverse relationship between thickness and surface roughness forultra-smooth PECVD SiO₂ film thickness up to approximately 3000 Å. Forcomparison purposes, curves 1204 and 1206 do not depict an inverserelationship between thickness and surface roughness data for theconventional silane-based and TEOS-based PECVD. When viewed in the lightof the direct relationship between thickness and roughness exhibited bythe conventional PECVD films individually (shown in FIG. 5), the datashown in FIG. 12 suggests that, unlike conventional PECVD films,increasing the thickness of some example ultra-smooth PECVD films maycomparatively improve the surface of a film stack relative to thesurface roughness of an underlying film.

In some embodiments, increasing the thickness of an ultra-smooth PECVDfilm may decrease the roughness of a film deposited on top of theultra-smooth PECVD film, as shown in the examples depicted in FIGS. 13and 14. FIG. 13 schematically shows film stack 1100 of FIG. 11,including example ultra-smooth PECVD SiO₂ film layer 1106, on top ofwhich an 800 Å-thick silicon nitride layer 1304 is deposited. FIG. 14shows a graph 1400 illustrating an inverse relationship 1402 between thethickness of layer 1106 and the roughness of surface 1308 of siliconnitride layer 1304. For example, for a 1000 Å thick ultra-smooth PECVDSiO₂ film layer 1106 underlying silicon nitride layer 1304, siliconnitride surface 1308 exhibits an absolute roughness of approximately12.6 Å, or approximately 77% as rough as silicon nitride layer 1104 andapproximately the same roughness as ultra-smooth PECVD SiO₂ film layer1106. For comparison, points 1404 and 1406 depict thickness-dependentroughness data for the conventional silane-based and TEOS-based PECVDprocesses, respectively, which are approximately 92% and 89% as rough aslayer 1304.

FIG. 15 shows a flow chart illustrating an example embodiment of amethod 1500 for depositing an ultra-smooth PECVD silicon-containingfilm. Method 1500 includes, at 1502, supplying a reactant gas orreactant gas mixture to a process station. At 1504, method 1500 includesmaintaining a capacitively-coupled plasma to generate radicals andactive species of the reactant gas and/or of inert gases included in thereactant gas mixture. At 1506, method 1500 includes, while depositing afilm on the substrate surface, controlling a process parameter tocontrol an absolute roughness of the film surface, as explained in moredetail below. For example, in some embodiments, one or more processparameters may be controlled during a film deposition phase so that theabsolute roughness of the film decreases with increasing thickness ofthe film. In another example, in some embodiments, one or more processparameters may be controlled during a film deposition phase so that theabsolute roughness is controlled to below a predetermined threshold. Inone scenario, for example, the absolute roughness of an ultra-smoothPECVD silicon-containing film having a refractive index of betweenapproximately 1.4 and 2.1 may be controlled to below 4.5 Å as measuredon a bare silicon substrate. It will be appreciated that processparameter control may be performed by any suitable controller includedin a process tool. Example controllers are described in more detailbelow.

While method 1500 refers to a method of depositing a single layer ofultra-smooth PECVD film, it will be appreciated that, in someembodiments, method 1500 may represent an ultra-smooth PECVD filmdeposition phase of an in-situ film stack deposition process. Thus, insome embodiments, a suitable number of instances of method 1500 may beperformed to build a film stack. In one example, layers of ultra-smoothPECVD undoped silicon films (discussed in more detail below) may bealternated with layers of ultra-smooth PECVD doped silicon films tobuild an ultra-smooth alternating undoped silicon/doped silicon filmstack. In another example, layers of ultra-smooth PECVD undoped siliconfilms may be alternated with layers of ultra-smooth PECVD silicondioxide films. Thus, in some embodiments, suitable ultra-smooth PECVDprocesses may be used to deposit each layer in a film stack. In onescenario, for example, layers of ultra-smooth silicon oxide may bealternated with layers of ultra-smooth silicon nitride. In anotherscenario, layers of ultra-smooth silicon oxide may be alternated withlayers of conventional silicon nitride film.

Alternatively, in other embodiments, a suitable number of instances ofmethod 1500 may be included, at one or more suitable intervals, withother suitable deposition processes (e.g., PECVD, CVD, or ALD processes)to build a film stack in-situ. In one example, an ultra-smooth PECVDsilicon dioxide film may be alternated with a PECVD silicon nitride filmto form an alternating silicon dioxide/silicon nitride film stacksimilar to that shown in FIG. 4. In another example, aconventionally-deposited film stack may be capped with a suitablethickness of an ultra-smooth PECVD film.

Further, it will be appreciated that, in some embodiments, adjusting thefilm stack deposition scheme may provide, on an in-situ basis,approaches to tune bulk properties of the film stack (e.g., wafer bow)while still providing an acceptable top surface roughness, and, in someembodiments, to provide ultra-smooth patterning surfaces while realizingfaster deposition rates for underlying layers.

Continuing with FIG. 15, various examples of approaches to control oneor more process parameters to control an absolute roughness of the filmsurface are described below with respect to an example ultra-smoothPECVD silicon dioxide film process. For example, an ultra-smooth silicondioxide film may be deposited using silane and nitrous oxide (N₂O) inone or more process stations of a process tool. Non-limiting examples ofprocess conditions for depositing ultra-smooth PECVD silicon dioxidefilms using an example four-station process tool (an embodiment of whichis described in more detail below) are provided in Table 1.

TABLE 1 Parameter Range Pressure (torr) 0.5-8.0 Temperature (° C.)300-600 He flow rate (sccm) 0-10000 Ar flow rate (sccm) 0-10000 Silaneflow rate (sccm) 10-200 N₂O flow rate (sccm) 1000-30000 Nitrogen flowrate (sccm) 0-20000 High-frequency plasma power (W) 500-5000Low-frequency plasma power (W) 0-2500 Time between beginning of silaneflow −3 to +3 and plasma ignition (sec) Time between end of silane flowand −3 to 10 plasma extinction (sec)

In some embodiments, controlling a process parameter to control anabsolute roughness of the film surface may include, at 1508, supplyingprocess gases, including one or more co-reactants and/or one or morediluents, to the process station at a concentration of at least 150times a concentration of a silicon-containing reactant included in thereactant gas mixture. In such embodiments, oversupplying the co-reactantmay create a plasma that is lean in silicon radicals, potentiallyreducing the deposition rate. By controlling the deposition rate to lessthan a threshold deposition rate, an ultra-smooth PECVD film may result.

For example, in the case of a silicon oxide film deposited using theexample process parameters described above, N₂O may be fed at a flowrate of from approximately 5 times an amount of the silane flow rate toapproximately 3000 times an amount of the silane flow rate. Assumingother process parameters are held constant, the greater flow rate of N₂Omay control the deposition rate of the silicon dioxide film to less than10 Å/sec. Such deposition rates may have surface rearrangement andassembly reactions at suitable rates to produce an ultra-smooth siliconoxide film having a roughness of less than or equal to 4.5 Å Ra forfilms of up to 3000 Å thickness or more as measured on a siliconsubstrate.

Previously, it was believed that reducing the flow rate of silane inconventional silane-based PECVD silicon dioxide deposition processeswould not result in a similar reduction in silicon dioxide filmroughness. Instead, the surface of the deposited film was believed tobecome rougher as the silane flow rate was reduced. FIG. 16 shows anexample relationship 1600 between surface roughness as measured by AFMand silane flow rate. FIG. 17 shows an example relationship 1700 betweensilane flow rate and silicon dioxide film deposition rate forrelationship 1600 shown in FIG. 16. For comparative purposes, an examplefilm deposited by the conventional silane-based PECVD process isindicated (points 1602 and 1702). FIGS. 16 and 17 graphically illustratethat roughness increases as the silane flow rate and the deposition ratedecrease from the conventional silane-based PECVD process.

However, referring to the left-most portion of FIG. 16, it has beenfound that controlling the deposition rate below a threshold level mayactually decrease surface roughness, which may allow ultra-smoothsilicon-containing surfaces to be obtained. Thus, FIGS. 16 and 17 showthat, in the embodiment depicted, reducing the flow rate of silane below100 sccm reduces the silicon dioxide deposition rate to below 10 Å/sec,in turn reducing the surface roughness of the silicon dioxide filmdeposited. As shown in FIGS. 16 and 17, in some embodiments, processesproviding a silicon dioxide deposition rate of less than 6 Å/sec mayproduce films having a roughness of less than or equal to 4.5 Å Ra forfilms of up to 3000 Å thickness or more as measured on a siliconsubstrate.

While the example described above refers to controlling the depositionrate by controlling a flow and/or concentration of silane, it will beappreciated that such effects may be achieved by controlling the flowand/or concentration of any suitable silicon-containing reactant.Non-limiting examples of suitable silicon-containing reactants that mayproduce ultra-smooth silicon-containing films include silanes (e.g.,Si_(x)H_(y), such as silane and disilane), halogen-substituted silanes(e.g., Si_(x)Cl_(y)), and alkyl-substituted silanes (e.g., Si_(x)R_(y)).

It will be appreciated that, in some embodiments, controlling the flowsand/or concentrations of other process gases (e.g., co-reactants, suchas N₂O, CO, and CO₂, and inerts, such as nitrogen, argon, and helium)may be used to control the deposition rate of the film to less than athreshold amount. For example, FIG. 18 shows a relationship 1800 betweenprocess station pressure and deposition rate for example ultra-smoothPECVD SiO₂ films deposited at a constant 100% SiH₄ flow rate of 40 sccm(though it will be appreciated that suitably dilute silane feed sourcesmay have a greater flow rate without departing from the scope of thepresent disclosure) but having different total gas flow rates.Specifically, points 1802 shows a deposition rate trend for an examplewhere the flow rates of all gases except silane are half thecorresponding flow rates for the example shown in points 1804. Despiteeffectively increasing the concentration of silane, in the example shownin FIG. 18, reducing the flow rate of inert and non-inert gases leads toa decrease in deposition rate and a reduction in film roughness of up to0.3 Å Ra (not shown) from the conditions of points 1804 to theconditions of points 1802. In another example, substituting CO or CO₂for N₂O, each of which may have a different ionization cross-sectionrelative to N₂O, may reduce the concentration of oxygen radicals in theplasma, potentially reducing the deposition rate of the silicon dioxidefilm.

As explained above, in some embodiments, and without wishing to be boundby theory, it is believed that decreasing the silane flow may provideadditional time for surface migration and cross-linking of varioussilane radical species. Increasing the time for such processes mayprovide structurally dense lattices with comparatively fewer defects,potentially resulting in a smoother surface topography.

For example, FIG. 19 illustrates a relationship 1900 between filmstress, deposition rate, and silane flow rate for an example silicondioxide film. As the deposition rate declines in the example shown inFIG. 19, the film stress becomes comparatively more compressive,suggesting that the film is structurally denser. FIG. 20 shows arelationship 2000 between film stress, substrate bow, and film thicknessfor an example ultra-smooth PECVD SiO₂ film deposited at approximately2.3 Å/sec. The example film shown in FIG. 20 exhibits a lineardependence 2002 of substrate bow on film thickness. The example filmshown in FIG. 20 also exhibits a non-linear relationship 2004 betweenfilm stress and film thickness. As shown in FIG. 20, the film stress forthe example film rapidly approaches the bulk film stress level withinthe first 1000 Å of deposition. Thus, the example ultra-smooth PECVDsilicon dioxide film shown in FIG. 20 may rapidly achieve structuralstability as the film is deposited.

Other structural analyses provide additional support for the suggestionthat increasing the time for surface rearrangement and assemblyreactions may provide structurally dense lattices with comparativelyfewer defects, potentially resulting in a smoother surface topography.For example, FIG. 21 shows a comparison of Fourier transform infrared(FTIR) spectra for an example thermally grown SiO₂ film (spectrum 2102)(sometimes called thermal oxide), an example ultra-smooth PECVD SiO₂film having a deposition rate of approximately 2.3 Å/sec (spectrum2104), and an example conventional TEOS-based PECVD SiO₂ film (spectrum2106). As shown in FIG. 21, the example ultra-smooth PECVD film has astructure and composition that is more like that of the thermal oxidethan the TEOS-based film is like that of the thermal oxide. For example,the peak height of the Si—O bond stretch mode for an exampleultra-smooth PECVD film is higher and narrower than the peak height ofthe Si—O bond stretch mode for the TEOS-based film for comparable filmthicknesses. This may suggest that there is a comparatively narrowerdistribution of bond types within the example ultra-smooth PECVD filmrelative to the TEOS-based film. Further, the position of the Si—O bondstretch mode for the ultra-smooth PECVD film shown in FIG. 21 (1071cm⁻¹) is closer to the Si—O bond stretch mode position for the thermaloxide (1078 cm⁻¹) than is the Si—O bond stretch mode for the TEOS-basedfilm (1063 cm⁻¹).

As further support for the suggestion that increasing the time forsurface rearrangement and assembly reactions may provide structurallydense lattices with comparatively fewer defects, potentially resultingin a smoother surface topography, the wet etch characteristics of someultra-smooth PECVD SiO₂ films approaches those of thermal oxides. Table2 includes wet etch rate ratio (WERR, defined as 1 for thermal oxide)data for various PECVD SiO₂ films in a dilute hydrofluoric acid bath(100:1 H₂O:HF). For comparison, WERR data for conventional silane-basedand TEOS-based PECVD processes and for a conventional HDP-CVD processare also included in Table 2. As shown in Table 2, the WERR for severalultra-smooth PECVD SiO₂ films is between 1.2 and 2.0.

TABLE 2 Deposition Film Process Rate WERR Ultra-smooth 2.3 Å/sec 1.2PECVD Ultra-smooth 6.1 Å/sec 2.0 PECVD Conventional — 1.7 TEOS-BasedPECVD Conventional — 4.0 silane-based PECVD Conventional — 1.4 HDP-CVDThermally — 1.0 grown oxide

Returning to FIG. 15, in some embodiments, controlling a processparameter to control an absolute roughness of the film surface mayinclude, at 1510, generating the plasma with a power density of 0.35W/in² or more. In some embodiments, such power densities may begenerated by a high-frequency plasma source operated at 250 W or more.As used herein, “high-frequency plasma” refers to a plasma operated at afrequency of 13.56 MHz or more. Additionally or alternatively, in someembodiments, a low frequency (e.g., frequencies below 13.56 MHz) powersource may be used. In some other embodiments, a dual-frequency plasmamay be used.

Table 3 provides example silicon dioxide film deposition and topographydata for a plurality of ultra-smooth PECVD SiO₂ films deposited at 550°C. using various high-frequency (HF) plasma powers on siliconsubstrates. While the example described herein refers to ahigh-frequency plasma, it will be appreciated that any suitable plasmaand/or power may be employed without departing from the scope of thepresent disclosure.

TABLE 3 HF 100% SiO₂ Dep. Power SiH₄ flow Thickness Rate Stress Ra (W)(sccm) (Å) (Å/sec) (MPa) (nm) 1000 40 1031 3.26 −254 0.304 1500 40 10192.76 −258 0.278 2000 40 1024 2.49 −268 0.275 2500 40 1030 2.34 −2680.263 3000 40 1023 2.24 −265 0.256 3500 40 1034 2.20 −267 0.252 4000 401015 2.19 −249 0.245 4500 40 1025 2.27 −267 0.245

FIG. 22 graphically illustrates a relationship 2200 betweenhigh-frequency plasma power and absolute roughness for the exampleultra-smooth PECVD silicon dioxide films provided in Table 3. As shownin FIG. 22, at low deposition rates, such as those corresponding to lowsilane flow rates, increasing the power of a high-frequency plasma mayreduce the absolute roughness of ultra-smooth PECVD SiO₂ films. In theexample shown in FIG. 22, the surface roughness of some ultra-smoothPECVD silicon dioxide films may be less than 2.5 Å as measured on asilicon substrate. As the native surface roughness of a typical siliconsubstrate approaches 2.5 Å, this may further suggest that such films arecapable of self-planarization.

Additionally or alternatively, in some embodiments, the plasmaconditions may be selected to control the ion density of the plasma.Continuing with FIG. 15, controlling a process parameter to control anabsolute roughness of the film surface may include, at 1512, maintainingan ion density of less than 2×10¹⁰ ions/cm³. For example, a plasma fordepositing an ultra-smooth PECVD silicon oxide film may be supplied at aplasma power of between 250 and 5000 watts and at a process stationpressure of between 0.5 and 8 torr. In some embodiments, such plasmapowers may generate a plasma density of between approximately 0.35 W/in²and 7.1 W/in² at four 15-inch showerheads powered by a shared plasmagenerator. This may avoid potential sputter-induced interlayer mixing infilm stack applications.

Continuing with FIG. 15, in some embodiments, controlling a processparameter to control an absolute roughness of the film surface mayinclude, at 1514, generating a plasma at a process station pressure ofapproximately 8 torr or less. In such embodiments, an ultra-smoothcharacteristic may be substantially maintained while a deposition ratefor a film is adjusted while maintaining the deposition rate at a ratebelow the threshold rate. Put another way, the deposition rate of thefilm may be adjusted by varying the process station pressure withoutsubstantially altering the ultra-smooth topography of a deposited film.

Thus, Table 4 shows example silicon dioxide film deposition andtopography data for a plurality of ultra-smooth PECVD SiO₂ filmsdeposited at 550° C. on silicon substrates using various process stationpressures.

TABLE 4 Pressure SiH₄ flow HF Power Thickness Dep. Rate Stress Ra (torr)(sccm) (W) (Å) (Å/sec) (MPa) (nm) 1.5 40 2500 985.2 6.22 −280 0.286 2 402500 978.5 5.66 −285 0.277 3 40 2500 1006.6 3.91 −286 0.263 4 40 25001018.4 2.84 −271 0.256 5 40 2500 1042.9 2.36 −268 0.271 6 40 2500 1030.92.11 −267 0.261

FIG. 23 illustrates a dependence 2300 of smoothness on process stationpressure using the example data of Table 4. As shown in FIG. 23,decreasing the pressure of the process station may correlate with aslight increase in surface roughness for the example ultra-smooth PECVDsilicon dioxide films, though the absolute roughness may still bemaintained at less than 3 Å Ra as measured on a silicon substrate. FIG.23 shows that surface smoothness may have a non-linear relationship withprocess station pressure during the example process range depicted, asshown in a minimum surface roughness at approximately 4 torr.

FIG. 24 shows a graph 2400 depicting a non-linear relationship betweenwithin-substrate range non-uniformity and process station pressure forthe example films shown in Table 4. Thus, it will be appreciated fromthe example data provided in Table 4 and FIGS. 23 and 24 that, in someembodiments, an ultra-smooth PECVD silicon oxide film characteristic maybe maintained and/or adjusted by generating the plasma at a processstation pressure 8 torr or less. In one example, the deposition rate maybe increased to greater than 6 Å/sec while maintaining a surfaceroughness of less than 3 Å (as measured on a 1000 Å film deposited on asilicon substrate). In another example, the within-substratenon-uniformity of a deposited film may be decreased to less than 3%while maintaining a surface roughness of less than 3 Å as measured on asilicon substrate.

In another example, an ultra-smooth characteristic may be substantiallymaintained while a deposition rate for the film is adjusted by varyingan amount of an inert gas to the process station. Thus, continuing withFIG. 15, in some embodiments, controlling a process parameter to controlan absolute roughness of the film surface may include, at 1516,supplying an inert gas to the plasma. For example, in some embodiments,argon may be supplied to the plasma to adjust the deposition rate of anultra-smooth PECVD silicon dioxide film.

FIG. 25 shows a relationship 2500 between deposition rate and argon flowrate to the process station for example ultra-smooth PECVD SiO₂ filmsdeposited at 550° C. on silicon substrates. FIG. 25 also shows arelationship 2502 between SiO₂ film stress and argon flow rate to theprocess station. As shown in FIG. 25, the deposition rate may beincreased and the SiO₂ film made more compressive, by increasing theflow rate of argon to the process station.

Further, in some embodiments, supplying inert gas to the process stationmay adjust the deposition rate without substantially disturbing thesurface roughness of the film. For example, FIG. 26 shows anapproximately constant relationship 2600 between absolute roughness andargon flow rate for the example ultra-smooth PECVD SiO₂ films shown inFIG. 25. Thus, it will be appreciated from the examples shown in FIGS.25 and 26 that, in some embodiments, the deposition rate of anultra-smooth PECVD film may be increased by increasing a flow rate ofargon to the process station without causing an increase in surfaceroughness. It will be appreciated that, in some embodiments, varying theflow rates of other suitable inert gases, such as nitrogen and helium,may have similar effects.

It will be appreciated that control of the surface smoothness viacontrol of one or more process parameters, such as reactant and inertfeed rates, plasma power, ion density, and process station pressure, maybe managed independently or in combination with any other suitableprocess variable. For example, in some embodiments, ion bombardment(e.g., from low-frequency plasma sources or from a DC bias sourceapplied to the plasma) may provide a suitable ultra-smoothsilicon-containing film. In another example, an ultra-smooth PECVD filmmay be deposited at temperatures of 400 C or greater. In one scenario,an ultra-smooth PECVD silicon dioxide film may be deposited at 550 C.Such films may exhibit the ultra-smooth surfaces described herein whilehaving comparatively lower hydrogen concentrations than films depositedat 400 C or less. Further, such films may maintain a substrate bowwithout the assistance of a subsequent annealing step. Such films mayexhibit ultra-smooth and highly flat surfaces during a subsequentlithography step where a pattern is transferred to the film stack. Othernon-limiting examples of other process variables include process stationtemperature, plasma ignition sequencing, plasma extinction sequencing,and a spacing between a process gas distribution showerhead and adeposition substrate surface. For example, in one scenario, ahigh-frequency plasma may be ignited before silane is introduced to theprocess station. This may condition the substrate surface for depositionprior to the beginning of deposition, which in turn may reduce theformation of surface islands or domains. In another scenario, ahigh-frequency plasma may be extinguished after flow rate of silane isstopped after deposition, to consume residual silane molecules in theprocess station.

While the examples above relate to the deposition of ultra-smooth PECVDsilicon dioxide films, it will be appreciated that any suitablesilicon-containing film may be deposited according to the embodimentsdescribed herein. In some embodiments, ultra-smooth PECVD siliconnitride films may be deposited by plasma-activated reaction of ammoniaand silane. Further, in some embodiments, suitable silicon oxynitridefilms may be deposited by plasma-activation of silane and N₂O in thepresence of a nitrogen plasma. Other suitable nitrogen-containingreactants include, but are not limited to, hydrazine and nitrogen/heliumgas mixtures.

Table 5 summarizes roughness, refractive index, and film stress data fora variety of ultra-smooth silicon nitride containing films having arefractive index ranging from approximately 1.4 to approximately 2.1.The film data presented in Table 5 was measured from 1000 Å filmsdeposited on silicon substrates, each film generated by feeding, for therespective film recipe, the indicated amounts of nitrous oxide orammonia to a nitrogen plasma at a constant silane flow rate, nitrogenflow (approximately 5000 sccm), helium flow (approximately 8000 sccm),pressure (approximately 5 torr) and high-frequency plasma power(approximately 4500 W). As indicated in Table 5, reducing the flow ofnitrous oxide fed to the plasma (shown in recipes A-G) provides a widerange of silicon oxide and silicon oxynitride films exhibiting anabsolute roughness of less than approximately 3.1 Å, and in many cases,less than approximately 2.7 Å.

TABLE 5 100% SiH₄ N₂O NH₃ flow flow flow Stress Refractive Ra RecipeName (sccm) (sccm) (sccm) (MPa) Index (nm) A 40 12000 0  −302 1.46170.235 B 40 8000 0  −313 1.4622 0.231 C 40 4000 0  −339 1.4615 0.249 D 401500 0  −348 1.4669 0.266 E 40 500 0  −355 1.4703 0.265 F 40 150 0  −3141.5051 0.269 G 40 80 0  −347 1.6214 0.309 H 40 0 0 −1824 1.992 0.755 I40 0 300 −1734 1.990 0.397 J 40 0 500 −1566 1.982 0.305 Conventional 9800 7500  +200 to 1.90−2.02 0.53 PECVD SiN  −200

FIG. 27 shows a graph 2700 illustrating a comparison of Fouriertransform infrared spectra showing Si—O bond stretching mode data forthe example ultra-smooth PECVD silicon oxide and oxynitride filmspresented in Table 5. The FTIR measurements shown in FIG. 27 show atransition in Si—O bond stretch peak position as the concentration ofnitrous oxide in the process station is reduced.

The measurements presented in Table 5 also illustrate that ultra-smoothPECVD silicon nitride films having absolute roughness values ofapproximately 4 Å or less may be deposited by substituting ammonia fornitrous oxide at suitable flow rates. The data presented in Table 5suggest an inverse relationship between film roughness and film stressand ammonia concentration. For comparison, film and recipe parametersfor a conventional PECVD silicon nitride process are also provided inTable 5. FIGS. 28-30 depict comparisons of FTIR spectra 2800, 2900, and3000, showing Si—N, N—H, and Si—H bond stretching modes, respectively,for the example ultra-smooth PECVD silicon nitride and conventionalPECVD silicon nitride films presented in Table 5. As shown in FIGS. 28and 29, increasing the ammonia concentration tends to shift the Si—Npeak position away from the Si—N peak position of the conventional filmand tends to increase the area of the N—H peak. This may suggestadditional hydrogen incorporation in the film and provide an approachfor tuning the film stress characteristics of the film, as supported bythe stress data included in Table 5. However, FIG. 30 shows that, unlikethe conventional PECVD film, the Si—H bond stretching mode is absent forthe ultra-smooth PECVD silicon nitride films. This may provide acomparative improvement in breakdown voltage characteristics for thefilm relative to the conventional PECVD silicon nitride. Thus, it willbe appreciated that, in some examples, the bulk film stresscharacteristics of the ultra-smooth PECVD silicon nitride film may betuned while preserving electrical characteristics of the film.

In another example, an ultra-smooth PECVD silicon film (e.g., anamorphous silicon film, an undoped polycrystalline silicon film or adoped polycrystalline silicon film) may be deposited from plasmadecomposition of silane alone or in a suitable reducing environment,such as in the presence of a helium, argon, and/or hydrogen plasma, and,in cases where doped polycrystalline silicon is deposited, in thepresence of a suitable dopant precursor (e.g., a boron-containingprecursor, an arsenic-containing precursor, and/or aphosphorous-containing precursor). Such ultra-smooth PECVD silicon filmsmay also be used to construct film stacks in-situ, and may also exhibitself-planarizing characteristics. Further, in some embodiments,ultra-smooth PECVD silicon processes may add a DC bias or anothersuitable ion bombardment approach to promote surface rearrangement andpotentially enhance surface smoothing. Non-limiting example processparameters for depositing ultra-smooth PECVD undoped silicon films usingan example four-station process tool (described in detail below) areshown in Table 6.

TABLE 6 Parameter Range Pressure (torr) 0.5 to 8.0 Temperature (° C.)300-650 He flow rate (sccm) 0-10000 Ar flow rate (sccm) 0-10000 100%Silane flow rate (sccm) 0.1-200 N₂O flow rate (sccm) 0-30000 Nitrogenflow rate (sccm) 0-15000 High-frequency plasma power (W) 250-5000Low-frequency plasma power (W) 0-2500 Time between beginning of silaneflow −3 to +3 and plasma ignition (sec) Time between end of silane flowand −3 to +10 plasma extinction (sec)

Further, in some embodiments, an ultra-smooth PECVD silicon film may bedoped by supplying a suitable dopant during deposition or in apost-deposition treatment phase. Non-limiting examples of dopantsinclude arsenic, boron, and phosphorous. In some embodiments, a dopedsilicon film may be activated by a suitable thermal anneal in-situ. Forexample, an ultra-smooth PECVD boron-doped silicon film deposited at550° C. may be annealed to 650° C. without a vacuum break. In someexamples, annealing a doped film may lower the resistance of the film,improve conductivity within the film and the film stack and/or reducethe amount of dopant needed to provide a selected film conductivity.

As explained above, ex-situ film processing may lead to the inclusion ofdefects at one or more interfacial boundaries within the film stack.However, in some scenarios, transitions between in-situ film depositionprocesses may also lead to defect generation. For example, smallparticle defects may be generated from the interaction of incompatibleprocesses gases during an in-situ transition from one film depositionprocess to another. Thus, various embodiments are disclosed herein thatare related to film deposition chemistries, hardware, and purgesequences used for in-situ transitions between sequentially depositedfilms.

In contrast with a CVD process, where thermally activated gas-phase orsurface-adsorbed decomposition and/or displacement reactions are used todeposit a film, a PECVD process supplements at least a portion of theprocess activation energy with plasma energy. Generally, plasma energymay refer to an energy associated with electrons, ions, excited species,and chemical radicals. In some embodiments, plasma-provided energy mayresult in lower deposition temperatures, which may extend thermalprocess budgets. Further, in some embodiments, PECVD processes mayprovide higher deposition rates, which may increase substrate throughputfor a process tool.

In some embodiments, plasmas for PECVD processes may be generated byapplying a radio frequency (RF) field to a low-pressure gas using twocapacitively coupled plates. Ionization of the gas between the plates bythe RF field ignites a plasma, creating free electrons in the plasmadischarge region. These electrons are accelerated by the RF field andmay collide with gas-phase reactant molecules. Collision of theseelectrons with reactant molecules may form radical species thatparticipate in the deposition process. In one example, reactant radicalsreact with surface-adsorbed co-reactants to deposit a film layer. Itwill be appreciated that the RF field may be coupled via any suitableelectrodes. Non-limiting examples of electrodes include process gasdistribution showerheads, substrate support pedestals, etc. Further, itwill be appreciated that plasmas for PECVD processes may be formed bysuitable processes other than capacitive coupling of an RF field to agas.

The plasma discharge region is surrounded by a negatively charged sheaththat confines the plasma discharge region. In some embodiments, tworadio frequency sources may be used concurrently to tune the plasma. Forexample, a low-frequency RF source may be used to control ion energy anda high-frequency RF source may be used to control plasma density.

In some embodiments, the plasma may be formed above the substratesurface, which may provide a greater plasma density and enhance a filmdeposition rate. However, small particles may form within the plasma.These small particles “float” electrically, so that electron and ioncurrents are balanced on the particle surface. Because an electrontypically has a higher mobility than an ion, the particle may becomenegatively charged. Consequently, these particles may be trapped atplasma-sheath boundaries, where molecular drag forces from neutral andionized species directed toward the deposition surface balanceelectrostatic forces directed toward the plasma discharge region.Quenching the plasma extinguishes the electrostatic forces, which maycause the particles to land on the deposition surface. Particles thatdecorate the deposition surface may appear as interface roughnessdefects or interface morphology defects and may ultimately diminishdevice performance and reliability.

Some approaches to mitigating defects created by plasma-generatedparticles include alternating pumping and purging of the reactorenvironment. However, these approaches may be time consuming and mayreduce tool throughput. Thus, various embodiments are disclosed hereinthat are related to maintaining plasma stability throughout in-situPECVD formation of film stacks to avoid depositing particles on thedeposition surface.

FIG. 31 shows a flow chart illustrating a method 3100 for depositing afilm stack in-situ using a plurality of plasma-activated film depositionphases. At 3102, method 3100 includes igniting a plasma. At 3104, method3100 includes, in a first plasma-activated film deposition phase,depositing a first layer of film having a first film composition. At3106, method 3100 includes sustaining the plasma while transitioning acomposition of the plasma from a first plasma composition of the firstplasma-activated film deposition phase to a second plasma composition ofthe second plasma-activated film deposition phase. At 3108, method 3100includes, in the second plasma-activated film deposition phase,depositing a second layer of film having a second film composition ontop of the first layer of film. At 3110, method 3100 includes quenchingthe plasma. While method 3100 depicts an example two-layer in-situ filmstack deposition process, it will be appreciated that, in someembodiments, three or more layers may be deposited by including asuitable number of film transition phases in which the plasma issustained while the plasma composition is altered without departing fromthe scope of the present disclosure.

FIG. 32 schematically shows an example process timing diagram 3200 forin-situ PECVD deposition of alternating layers of silicon nitride andsilicon oxide films. In the example shown in FIG. 32, silicon nitride isdeposited by reaction of silane (SiH₄) and ammonia (NH₃) in the presenceof a plasma during a first film deposition phase and silicon dioxide isdeposited by reaction of silane and nitrous oxide (N₂O) in the presenceof a plasma during a second film deposition phase. As shown in theexample depicted in FIG. 32, a plasma is sustained during transitionsbetween deposition phases. Sustaining the plasma may trapplasma-generated particles in the above-described electrically floatingstate. Trapping the particles in the sustained plasma may reducedecoration of the surface by small particle defects, which may lead toincreased yields compared to processes in which the plasma is quenchedbetween deposition steps.

In some embodiments, the plasma is sustained by controlling processstation conditions to maintain a constant plasma volume (e.g., less than20% variation as the plasma volume is visually observed) betweendifferent and/or subsequent deposition events. Alternatively oradditionally, in some embodiments, a constant ion energy distributionand/or a constant absorbed RF power distribution is maintained betweensubsequent deposition events. In some embodiments, such control may beachieved by controlling one or more set points of a process stationpressure, a gas concentration, an RF source power, an RF sourcefrequency, and a plasma power pulse timing. In one non-limiting example,a set point for a total delivered plasma power may be held constantbetween different film deposition events. In another non-limitingexample, a low-frequency plasma power may be decreased by aproportionally greater amount than a decrease in a high-frequency plasmapower. This may reduce ion damage to the substrate surface betweendeposition events while maintaining plasma density. It will beappreciated that such parameters may be adjusted, discretely orcontinuously, to maintain plasma stability and to avoid indicia ofplasma instability. Non-limiting examples of indicia of plasmainstability include plasma flickering, extinction, and local plasmabrightness variation. It further will be appreciated that these specificembodiments are described for the purpose of example and are notintended to be limiting, as any suitable method of maintaining plasmaintegrity and stability may be employed between various depositionphases of an in-situ PECVD film stack process.

FIG. 32 shows an example list of parameters 3222, such as gas flowrates, process pressure, and high- and low-frequency RF power settingsfor an RF power source that may be used in an in-situ PECVD processincluding sustained plasmas between deposition events. FIG. 32 alsoshows a temporal progression of process phases, wherein one or more ofparameters 3222 are varied to achieve a process condition for theprocess phase. Each of the example process phases will be described indetail below, though it will be appreciated that other suitable processchemistries may vary one or more aspects of the process phases whileremaining within the scope of the present disclosure. Parameter rangesfor example silane-based silicon dioxide and silicon nitride processesusing an example four-station process tool (described in more detailbelow) are provided in Tables 7A and 7B, though it will be appreciatedthat other suitable parameter ranges may be employed in otherembodiments of film-forming process chemistries. For example, otherparameter ranges may apply for silicon dioxide films formed from silaneusing CO and/or CO₂ as an oxygen source and for silicon nitride filmsformed from silane using nitrogen atoms obtained from N₂ and/or N₂/H₂plasmas. An example silicon nitride process using silane and ammonia andan example four-station process tool is provided in Table 8 and anexample silicon dioxide process using silane and nitrous oxide and anexample four-station process tool is provided in Table 9.

TABLE 7A Silicon Silicon Silicon nitride nitride nitride depositiondeposition deposition N/O preparation subphase subphase transition Phasephase 1 2 phase SiH₄ 1-1000 1-1000 1-1000 0-1000 (sccm) N₂ 0-100000-10000 0-10000 0-20000 Manifold A (sccm) NH₃ 10-10000 10-10000 10-100000-10000 (sccm) N₂O 0 0 0 0-30000 (sccm) N₂ 0-20000 0-20000 0-200000-20000 Manifold B (sccm) He (sccm) 0-20000 0-20000 0-20000 0-20000 Ar(sccm) 0-30000 0-30000 0-30000 0-30000 Pressure 0.5-6.0 0.5-6.0 0.5-6.00.5-6.0 (torr) Temp (C.) 200-650 200-650 200-650 200-650 HF 0-50000-5000 0-5000 0-5000 Power (W) LF 0-2500 0-2500 0-2500 0-2500 Power (W)

TABLE 7B SiO₂ SiO₂ SiO₂ deposition deposition deposition O/N preparationsubphase subphase transition Phase phase 1 2 phase SiH₄ 0.1-10000.1-1000 0.1-1000 0-1000 (sccm) N₂ 0-20000 0-20000 0-20000 1000-10000Manifold A (sccm) NH₃ 0 0 0 0-10000 (sccm) N₂O 1-30000 1-30000 1-30000 0(sccm) N₂ 0-20000 0-20000 0-20000 0-20000 Manifold B (sccm) He (sccm)0-20000 0-20000 0-20000 0-20000 Ar (sccm) 0-30000 0-30000 0-300000-30000 Pressure 0.5-5.0 0.5-6.0 0.5-6.0 0.5-6.0 (torr) Temp (C.)200-650 200-650 200-650 200-650 HF 0-5000 0-5000 0-5000 0-5000 Power (W)LF 0-2500 0-2500 0-2500 0-2500 Power (W)

TABLE 8 SiH₄ (sccm) 200 NH₃ (sccm) 1040 N₂ Manifold A 6000 (sccm) N₂Manifold B 3000 (sccm) He (sccm) 0 Ar (sccm) 0 Pressure (torr) 2.8 Temp(C.) 550 HF Power (W) 1000 LF Power (W) 100

TABLE 9 SiH₄ (sccm) 40 N₂O (sccm) 24000 N₂ Manifold A 5000 (sccm) N₂Manifold B 5000 (sccm) He (sccm) 8000 Ar (sccm) 0 Pressure (torr) 1.5Temp (C.) 550 HF Power (W) 2500 LF Power (W) 0

At silicon nitride deposition preparation phase 3224 of FIG. 32, a flowrate for silane is set and silane is supplied to a process stationbypass line. This may provide time for the silane flow to stabilizeprior to introduction to the process station. FIG. 32 also shows thatammonia is supplied to the process station at a controlled flow rate.Thus, each reactant for the silicon nitride deposition process may beflow-stabilized prior to initiating deposition, which may provide fordeposition thickness control during the silicon nitride depositionprocess. FIG. 32 also shows that nitrogen is supplied to the processstation during silicon nitride deposition preparation phase 3224.Nitrogen may act as a diluent gas to assist pressure and/or temperaturecontrol, as a sweep gas to prevent back-diffusion of reactant gases intoplumbing for an incompatible co-reactant, etc. Additionally oralternatively, in some embodiments, nitrogen may react with silane toform a silicon nitride film.

FIG. 32 also shows that other process variables are set and stabilizedduring silicon nitride deposition preparation phase 3224. For example,helium is supplied to the process station and a high frequency RF powersource is activated to strike and stabilize a helium plasma. Further, aprocess station pressure is stabilized during silicon nitride depositionpreparation phase 3224. In some embodiments, process station pressuremay be controlled by varying one or more gas flows feeding the processstation, adjusting a process station throttle valve, etc. Further, insome embodiments, a temperature of a substrate pedestal may bestabilized at a deposition temperature. Thus, it will be appreciatedthat any suitable process parameter may be adjusted and/or stabilized atsilicon nitride deposition preparation phase 3224. Silicon nitridedeposition preparation phase 3224 may have any suitable duration. In onenon-limiting example, silicon nitride deposition preparation phase 3224may be approximately three seconds long.

The process station begins depositing silicon nitride at silicon nitridedeposition phase 3226. In the example shown in FIG. 32, silicon nitridedeposition phase 3226 is divided into two subphases: nitride depositionsubphase 3226A, which represents an active deposition subphase, andnitride deposition subphase 3226B, which represents a post-depositionfilm treatment subphase.

As shown in FIG. 1, silane, which was previously routed to the processstation bypass line, is supplied to the process station and thelow-frequency RF power is increased during nitride deposition subphase3226A. Consequently, a silicon nitride film is nucleated and iscontinuously deposited on the substrate surface throughout nitridedeposition subphase 3226A. Excluding a time needed for film nucleation,the duration of nitride deposition subphase 3226A may be approximatelyproportional to the thickness of the deposited film. Thus, the durationof nitride deposition subphase 3226A may be adjusted to vary thethickness of the deposited silicon nitride layer. In one non-limitingexample, nitride deposition subphase 3226A may be approximately tenseconds long, which may correspond to a silicon nitride filmapproximately 300 angstroms thick.

At nitride deposition subphase 3226B, shown in FIG. 32, silane is againdiverted to the process station bypass line and the low-frequency RFpower is decreased. Further, ammonia flow to the process station isdecreased and the total process station pressure is reduced. In someembodiments, these adjustments may provide a post-deposition treatmentof bulk and/or near-surface portions of the deposited silicon nitridefilm. Example post-deposition treatments include a densificationtreatment and a nitrogen enrichment treatment. Additionally oralternatively, in some embodiments, nitride deposition subphase 3226Bmay provide a surface pre-treatment for preparing the silicon nitridesurface for subsequent film deposition. An example pre-treatment may beconfigured to reduce subsequent film nucleation time. Nitride depositionsubphase 3226B may have any suitable duration. For example, in oneembodiment, nitride deposition subphase 3226B may be approximately fiveseconds long. Further, it will be appreciated that additional nitridedeposition subphases may be included in some embodiments within thescope of the present disclosure.

At nitride/oxide transition phase 3228, shown in FIG. 32, variousprocess parameters are adjusted to transition the process station fromsilicon nitride deposition to silicon dioxide deposition. In the exampleshown in FIG. 32, the flow rate of silane, still routed to the processstation bypass line, is decreased. Further, the ammonia flow is turnedoff and an N₂O flow is turned on during nitride/oxide transition phase3228. Further still, sources of nitrogen are varied between gasmanifolds as shown in FIG. 32. As described above, sources and/or flowrates of nitrogen gas may be varied to provide back-diffusionprevention, pressure control, temperature control, etc. In someembodiments, nitrogen flow rates may be varied during nitride/oxidetransition phase 3228 to purge incompatible reactant gases from theprocess station that might otherwise participate in undesirabledefect-forming reactions.

Throughout nitride/oxide transition phase 3228, parameters 3222 arevaried to maintain the plasma. For example, FIG. 32 shows that thehelium flow is increased and high-frequency plasma power is decreased atnitride/oxide transition phase 3228. Similar plasma-stabilizingapproaches are used in silicon dioxide deposition preparation phase3230, where the HF power is increased in preparation for silicon dioxidedeposition phase 3232. These approaches may maintain the integrity andstability of the plasma density and/or volume during transition toprocess conditions for silicon dioxide film deposition. Non-limitingexamples of suitable durations of nitride/oxide transition phase 3228and silicon dioxide deposition preparation phase 30 are eachapproximately three seconds.

As shown in FIG. 32, silicon dioxide deposition phase 3232 is dividedinto two subphases. Oxide deposition subphase 3232A represents an activedeposition subphase. Oxide deposition subphase 3232B represents apost-deposition film treatment subphase. As shown in FIG. 32, silane,which was previously routed to the process station bypass line, issupplied to the process station during oxide deposition subphase 3232A.During oxide deposition subphase 3232A, a silicon dioxide film isnucleated and deposited on the substrate surface. Excluding a timeneeded for film nucleation, the duration of oxide deposition subphase3232A may be approximately proportional to the thickness of thedeposited film. Thus, the duration of oxide deposition subphase 3232Amay be adjusted to vary the thickness of the silicon dioxide layer. Inone non-limiting example, oxide deposition subphase 3232A may beapproximately eight seconds long, which may correspond to a depositedsilicon dioxide film approximately 300 angstroms thick.

At oxide deposition subphase 3232B, silane is diverted to the processstation bypass line and the high-frequency power is decreased. In someembodiments, these adjustments may provide a post-deposition treatmentof bulk and/or near-surface portions of the deposited silicon dioxidefilm. Example post-deposition treatments may include densificationtreatments, oxygen enrichment treatments, trap reduction treatments,etc. Additionally or alternatively, oxidation deposition subphase 3232Bmay pre-treat the surface of the deposited silicon dioxide inpreparation for deposition of a subsequent film. One examplepre-treatment may be a treatment to reduce subsequent film nucleationtime. Oxide deposition subphase 3232B may have any suitable duration. Inone non-limiting example, oxide deposition subphase 3232B isapproximately two seconds long. Further, it will be appreciated thatadditional oxide deposition subphases may be provided within the scopeof the present disclosure.

At oxide/nitride transition phase 3234, shown in FIG. 32, variousprocess parameters are adjusted to transition the process station fromsilicon dioxide deposition to silicon nitride deposition. In the exampleshown in FIG. 32, the flow rate of silane, still routed to the processstation bypass line, is increased. Further, the N₂O flow is turned offduring oxide/nitride transition phase 3234. Further still, sources ofnitrogen are varied between gas manifolds during oxide/nitridetransition phase 3234. As described above, sources and/or flow rates ofnitrogen gas may be varied to provide back-diffusion prevention,pressure control, temperature control, etc. In some embodiments,nitrogen flow rates may be varied during oxide/nitride transition phase3234 to purge incompatible reactant gases from the process station thatmight otherwise participate in undesirable defect-forming reactions.

Throughout oxide/nitride transition phase 3234, parameters 3222 arevaried to maintain plasma stability. For example, in the depictedembodiment, the helium flow is decreased and the high-frequency RF poweris increased at oxide/nitride transition phase 3234. This may maintainthe integrity and stability of the plasma density and/or volume duringtransition to process conditions for silicon dioxide film deposition.Oxide/nitride transition phase 3234 may have any suitable duration. Inone non-limiting example, oxide/nitride transition phase 3234 isapproximately two seconds long.

In some process conditions, high-frequency plasmas may be comparativelymore effective at bond scission processes than low-frequency plasmas.Conversely, under some process conditions, low-frequency plasmas mayprovide a comparatively higher flux of radicals to the substratesurface. Thus, it will be appreciated that, in some embodiments, plasmapowers for single or dual-frequency plasmas may be selected to generatesuitable plasma conditions for various film deposition chemistries andconditions. Example silicon oxide process conditions and silicon nitrideconditions suitable for use with the process illustrated in FIG. 32 areprovided in Tables 7A, 7B, 8 and 9 above.

It will be appreciated that the two-film process described above maycommence with the deposition of a silicon dioxide film rather than asilicon nitride film. Further, it will be appreciated that additionalalternating layers may be formed by repeating all or a part of theexample two-film process described above. For example, anoxide/nitride/oxide film may be deposited as a part of a process to forma silicon oxide/silicon nitride/silicon oxide (ONO) gate device. Furtherstill, it will be appreciated that, in some embodiments, multiple filmtypes may be deposited in-situ. For example, a three-film process may beused for in-situ deposition of a film stack having three film types.

While the deposition processes disclosed above have been discussed inthe context of 3D memory applications, it will be appreciated thatin-situ deposition of film stacks may be used for any suitable purposein an integrated device or in an integrated material. For example, acarbon-based ashable hardmask (AHM) layer may be deposited in-situ withan antireflective layer (ARL) for lithographic patterning applications.In one scenario, the ashable hardmask layer may be approximately 200 Åthick and the antireflective layer may be approximately 100 to 600 Åthick.

In another example, a carbon-doped silicon dioxide film may be depositedin-situ with a silicon nitride film using a suitable carbon-basedsilicon-containing reactant. For example, carbon-doped silicon dioxidefilms may be deposited using plasma-enhanced decomposition of TEOS(and/or another suitable alkoxysilane) in the presence of an oxygenplasma. In some embodiments, varying the concentration of oxygenradicals provided by the plasma may be used to vary an amount of carbonremaining in the silicon dioxide film. Thus, varying the plasmaconditions in a TEOS-based process may be used to modify physical andelectrical properties of the deposited silicon dioxide film that mightbe invariant in a silane-based silicon dioxide deposition process.

Parameter ranges for an example TEOS-based silicon dioxide process andan example silane-based silicon nitride process using an examplefour-station process tool (described in more detail below) are providedin Tables 10A and 10B. Table 11 shows a specific example of a TEOS-basedsilicon dioxide process using an example four-station process tool. Itwill be appreciated that other suitable parameter ranges may be employedin other embodiments of film-forming process chemistries. For example,other parameter ranges may apply for silicon dioxide films formed fromTEOS using N₂O (examples of which are described in more detail belowwith respect to Tables 12A, 12B, and 13), CO, and/or CO₂ as an oxygensource.

TABLE 10A Silicon Silicon Silicon nitride nitride nitride depositiondeposition deposition N/O preparation subphase subphase transition Phasephase 1 2 phase SiH₄ 1-1000 1-1000 1-1000 0 (sccm) TEOS 0 0 0 0-20(mL/min) N₂ 0-10000 0-10000 0-10000 0-10000 Manifold A (sccm) NH₃10-10000 10-10000 10-10000 0-10000 (sccm) O₂ 0 0 0 0-20000 (sccm) N₂0-20000 0-20000 0-20000 0-30000 Manifold B (sccm) He (sccm) 0-200000-20000 0-20000 0-20000 Ar (sccm) 0-30000 0-30000 0-30000 0-30000Pressure 0.5-6.0 0.5-6.0 0.5-6.0 0.5-6.0 (torr) Temp (C.) 200-650200-650 200-650 200-650 HF 0-5000 0-5000 0-5000 0-5000 Power (W) LF0-2500 0-2500 0-2500 0-2500 Power (W)

TABLE 10B SiO₂ SiO₂ SiO₂ deposition deposition deposition O/Npreparation subphase subphase transition Phase phase 1 2 phase SiH₄ 0 00 0 (sccm) TEOS 1-20 1-20 1-20 0 (mL/min) N₂ 0 0 0 0-10000 Manifold A(sccm) NH₃ 0 0 0 0 (sccm) O₂ 100-20000 100-20000 100-20000 0 (sccm) N₂ 00 0 0-20000 Manifold B (sccm) He (sccm) 0-20000 0-20000 0-20000 0-20000Ar (sccm) 0-30000 0-30000 0-30000 0-30000 Pressure 0.5-6.0 0.5-6.00.5-6.0 0.5-6.0 (torr) Temp (C.) 200-650 200-650 200-650 200-650 HF0-5000 0-5000 0-5000 0-5000 Power (W) LF 0-2500 0-2500 0-2500 0-2500Power (W)

TABLE 11 TEOS 4.5 (mL/min) O₂ (sccm) 10000 N₂ Manifold A 0 (sccm) N₂Manifold B 0 (sccm) He (sccm) 0 Ar (sccm) 0 Pressure (torr) 1.2 Temp(C.) 550 HF Power (W) 350 LF Power (W) 800

FIG. 33 schematically shows an example process timing diagram 3300 forin-situ PECVD deposition of alternating layers of silicon nitride andsilicon oxide films. In the example shown in FIG. 33, silicon nitride isdeposited by reaction of silane (SiH₄) and ammonia (NH₃) in the presenceof a plasma during a first film deposition phase and silicon dioxide isdeposited by reaction of TEOS and oxygen in the presence of a plasmaduring a second film deposition phase. As shown in the example depictedin FIG. 33 and described in more detail below, the plasma is quenchedduring transitions between silicon nitride and silicon dioxidedeposition phases.

At silicon nitride deposition preparation phase 3324 of FIG. 33, a flowrate for silane is set and silane is supplied to a process stationbypass line. This may provide time for the silane flow to stabilizeprior to introduction to the process station. FIG. 33 also shows thatammonia is supplied to the process station at a controlled flow rate.Thus, each reactant for the silicon nitride deposition process may beflow-stabilized prior to initiating deposition, which may provide fordeposition thickness control during the silicon nitride depositionprocess. FIG. 33 also shows that nitrogen is supplied to the processstation during silicon nitride deposition preparation phase 3324.Nitrogen may act as a diluent gas to assist pressure and/or temperaturecontrol, as a sweep gas to prevent back-diffusion of reactant gases intoplumbing for an incompatible co-reactant, etc. Additionally oralternatively, in some embodiments, nitrogen may react with silane toform a silicon nitride film. Other suitable process gases may besupplied to the process station in preparation for silicon nitridedeposition during silicon nitride deposition preparation phase 3324. Forexample, FIG. 33 also shows that helium is supplied to the processstation during silicon nitride deposition preparation phase 3324.

Other process parameters, such as process pressure, may also be adjustedduring silicon nitride preparation phase 3324. In some embodiments,process station pressure may be controlled by varying one or more gasflows feeding the process station, adjusting a process station throttlevalve, etc. Further, in some embodiments, a temperature of a substratepedestal may be stabilized at a deposition temperature. Thus, it will beappreciated that any suitable process parameter may be adjusted and/orstabilized at silicon nitride deposition preparation phase 3324. Siliconnitride deposition preparation phase 3324 may have any suitableduration.

In the example shown in FIG. 33, high and low frequency RF power sourcesare activated to strike and stabilize a plasma at an optional nitrideplasma ignition phase 3325, though it will be appreciated that in someembodiments, a single-frequency RF power source may be activated withoutdeparting from the scope of the present disclosure. Striking a plasmaprior to introducing silane to the process station may avoid smallparticle generation under some process conditions. For example, by firststriking a plasma and later supplying silane, as shown in FIG. 33,plasma ignition events that may generate small particles may becomparatively reduced relative to striking a silane plasma. However, itwill be appreciated that, in some embodiments, a silane plasma may beignited during silicon nitride deposition phase 3326.

The process station begins depositing silicon nitride at silicon nitridedeposition phase 3326. In the example shown in FIG. 33, silicon nitridedeposition phase 3326 is divided into two subphases: nitride depositionsubphase 3326A, which represents an active deposition subphase, andoptional nitride deposition subphase 3326B, which represents apost-deposition film treatment subphase.

As shown in FIG. 33, silane, which was previously routed to the processstation bypass line, is supplied to the process station during nitridedeposition subphase 3326A. Consequently, a silicon nitride film isnucleated and is deposited on the substrate surface throughout nitridedeposition subphase 3326A. Excluding a time needed for film nucleation,the duration of nitride deposition subphase 3326A may be approximatelyproportional to the thickness of the deposited film. Thus, the durationof nitride deposition subphase 3326A may be adjusted to vary thethickness of the deposited silicon nitride layer.

At nitride deposition subphase 3326B, shown in FIG. 33, silane isdiverted to the process station bypass line. In the embodiment shown inFIG. 33, the high- and low-frequency power supplies are turned off atthe end of nitride deposition subphase 3326B, which may consume residualsilane within the process station, potentially reducing small particledefects. However, it will be appreciated that, in other embodiments, oneor more of the plasma power supplies may be turned off at any suitablepoint within nitride deposition subphase 3326B.

In some embodiments, other process parameters, such as ammonia flow,process station pressure, and process station temperature, may beadjusted during nitride deposition subphase 3326B to provide apost-deposition treatment of bulk and/or near-surface portions of thedeposited silicon nitride film. Example post-deposition treatmentsinclude, but are not limited to, plasma and/or thermally-drivendensification treatments and nitrogen enrichment treatments.Additionally or alternatively, in some embodiments, nitride depositionsubphase 3326B may provide a surface pre-treatment for preparing thesilicon nitride surface for subsequent film deposition. An examplepre-treatment may be configured to reduce subsequent film nucleationtime. Nitride deposition subphase 3326B may have any suitable duration.Further, it will be appreciated that additional nitride depositionsubphases may be included in some embodiments without departing from thescope of the present disclosure. In the example shown in FIG. 33,silane, ammonia, and helium flows to the process station are turned offat the end of nitride deposition subphase 3326B in preparation for oxidedeposition.

At nitride/oxide transition phase 3328, shown in FIG. 33, variousprocess parameters are adjusted to transition the process station fromsilicon nitride deposition to silicon dioxide deposition. For example,FIG. 33 shows that nitrogen continues to flow in the process station toassist with purging residual silane and nitride deposition byproducts.In some embodiments, nitrogen flow rates may be varied duringnitride/oxide transition phase 3328 to purge incompatible reactant gasesfrom the process station that might otherwise participate in undesirabledefect-forming reactions. It will be appreciated that any suitable purgegas may be used without departing from the scope of the presentdisclosure, and that, in some embodiments, alternating purge andevacuation cycles may be used in nitride/oxide transition phase 3328 toprepare the process station for in situ silicon dioxide deposition. Inthe example shown in FIG. 33, nitrogen is turned off at the end ofnitride/oxide transition phase 3328.

Oxygen is supplied to the process station at the start of silicondioxide deposition preparation phase 3330. Subsequently, the exampleshown in FIG. 33 shows that, during optional oxide plasma ignition phase3331, both high and low frequency RF power sources are activated tostrike and stabilize a plasma. However, it will be appreciated that insome embodiments, a single-frequency power source maybe employed withoutdeparting from the scope of the present disclosure. It will beappreciated that oxide plasma ignition phase 3331 is optional, and that,in some embodiments, a plasma may be ignited during silicon dioxidedeposition phase 3332. In some embodiments, other gases, such as heliumand argon, may be provided to the process station during one or more ofsilicon dioxide deposition preparation phase 3330, optional oxide plasmaignition phase 3331 and subsequent silicon dioxide deposition phase3332.

The process station begins depositing silicon dioxide at silicon dioxidedeposition phase 3332. As shown in FIG. 33, silicon dioxide depositionphase 3332 is divided into two subphases. Oxide deposition subphase3332A represents an active deposition subphase. Optional oxidedeposition subphase 3332B represents a post-deposition film treatmentsubphase. As shown in FIG. 33, TEOS is supplied to the process stationduring oxide deposition subphase 3332A. During oxide deposition subphase3332A, a silicon dioxide film is nucleated and deposited on thesubstrate surface. Excluding a time needed for film nucleation, theduration of oxide deposition subphase 3332A may be approximatelyproportional to the thickness of the deposited film. Thus, the durationof oxide deposition subphase 3332A may be adjusted to vary the thicknessof the silicon dioxide layer. TEOS flow to the process station isstopped at the end of oxide deposition subphase 3332A.

In the example shown in FIG. 33, both high and low frequency powersupplies are turned off at the end of oxide deposition subphase 3332B.However, it will be appreciated that, in some embodiments, one or moreof the plasma power supplies may be turned off at any suitable pointwithin oxide deposition subphase 3332B. The resulting plasma may consumeresidual TEOS in the process station and may provide a post-depositiontreatment of bulk and/or near-surface portions of the deposited silicondioxide film. Example post-deposition treatments may includedensification treatments, oxygen enrichment treatments, trap reductiontreatments, etc. Oxygen flow to the process station is turned off at theend of oxide deposition subphase 3332B. At oxide/nitride transitionphase 3334, shown in FIG. 33, the flows of nitrogen and helium areturned on in preparation for a subsequent deposition of silicon nitride.

Additionally or alternatively, in some embodiments, particle generationcaused by incompatible process gases may be addressed by reacting TEOSwith plasma-activated nitrous oxide in place of plasma-activated oxygento form a silicon dioxide film. N₂O may be less likely to interact withthe silane-based silicon nitride process; for example, N₂O may be lesslikely to remain adsorbed to hardware and/or plumbing surfaces.Accordingly, an N₂O- and TEOS-based silicon dioxide process may be lesslikely to generate particles when sharing hardware with a silane-basedsilicon nitride process.

Parameter ranges for example N₂O- and TEOS-based silicon dioxideprocesses and example silane-based silicon nitride processes using anexample four-station process tool (described in more detail below) areprovided in Tables 12A and 12B. Table 13 shows a specific example of aN₂O- and TEOS-based silicon dioxide process using an examplefour-station process tool. It will be appreciated that other suitableparameter ranges may be employed in other embodiments of film-formingprocess chemistries. For example, other parameter ranges may apply forsilicon dioxide films formed from TEOS using CO and/or CO₂ as an oxygensource.

TABLE 12A Silicon Silicon Silicon nitride nitride nitride depositiondeposition deposition N/O preparation subphase subphase transition Phasephase 1 2 phase SiH₄ 1-1000 1-1000 1-1000 0 (sccm) TEOS 0 0 0 0-20(mL/min) N₂ 0-10000 0-10000 0-10000 0 Manifold A (sccm) NH₃ 10-1000010-10000 10-10000 0-10000 (sccm) N₂O 0 0 0 0-30000 (sccm) N₂ 0-200000-20000 0-20000 0-30000 Manifold B (sccm) He (sccm) 0-20000 0-200000-20000 0-20000 Ar (sccm) 0-30000 0-30000 0-30000 0-30000 Pressure0.5-6.0 0.5-6.0 0.5-6.0 0.5-6.0 (torr) Temp (C.) 200-650 200-650 200-650200-650 HF 0-5000 0-5000 0-5000 0-5000 Power (W) LF 0-2500 0-2500 0-25000-2500 Power (W)

TABLE 12B SiO₂ SiO₂ SiO₂ deposition deposition deposition O/Npreparation subphase subphase transition Phase phase 1 2 phase SiH₄ 0 00 0 (sccm) TEOS 1-20 1-20 1-20 0 (mL/min) N₂ 0 0 0 0-10000 Manifold A(sccm) NH₃ 0 0 0 0 (sccm) N₂O 100-30000 100-30000 100-30000 0-30000(sccm) N₂ 0 0 0 0-20000 Manifold B (sccm) He (sccm) 0-20000 0-200000-20000 0-20000 Ar (sccm) 0-30000 0-30000 0-30000 0-30000 Pressure0.5-6.0 0.5-6.0 0.5-6.0 0.5-6.0 (torr) Temp (C.) 200-650 200-650 200-650200-650 HF 0-5000 0-5000 0-5000 0-5000 Power (W) LF 0-2500 0-2500 0-25000-2500 Power (W)

TABLE 13 TEOS 4.9 (mL/min) N₂O (sccm) 15000 N₂ Manifold A 0 (sccm) N₂Manifold B 0 (sccm) He (sccm) 0 Ar (sccm) 0 Pressure (torr) 1.8 Temp(C.) 400 HF Power (W) 350 LF Power (W) 800

It will be appreciated that silicon oxide films deposited using plasmaactivated TEOS and nitrous oxide may be deposited by one or more of theembodiments described above. For example, in some embodiments, a siliconoxide film may be deposited on a substrate using TEOS and nitrous oxidein a process station. The process station may be controlled withinsuitable process parameter ranges such as those listed above in Tables12A, 12B, and 13. For example, a process station may be controlled toheat a substrate to a temperature of between 200° C. and 650° C.Deposition of the silicon oxide film may be achieved by supplying aplasma to the substrate and by supplying tetraethyl orthosilicate (TEOS)and nitrous oxide to the plasma.

As explained above, in some embodiments, silicon oxide films depositedby plasma-activation of TEOS and nitrous oxide may be performed in-situwith another deposition process. For example, in some embodiments, aprocess tool may deposit a silicon nitride film on a substrate followedby deposition of a silicon oxide film using plasma-activated TEOS andnitrous oxide without an intervening vacuum break. In one scenario, thein-situ deposition may occur within the same process station. In anotherscenario, the in-situ deposition may occur within different processstations included in the same process tool.

As explained above, in some embodiments, variations in the concentrationof oxygen radicals provided by the plasma may be used to vary an amountof carbon remaining in the silicon dioxide film. Thus, in someembodiments, varying the plasma conditions in a nitrous oxide- andTEOS-based plasma-activated film deposition process may be used toadjust the carbon concentration of the silicon oxide film in anysuitable way. For example, in some embodiments, the plasma may becontrolled to maintain an approximately constant concentration ofcarbon. Alternatively, in some embodiments, the plasma may be controlledto vary a carbon concentration profile as the film is deposited. Suchapproaches may vary physical and electrical properties of the depositedsilicon oxide film that might be invariant in a silane-based silicondioxide deposition process.

Additionally or alternatively, in some embodiments, in-situ filmtransitions may be made between film deposition processes by segregatingincompatible process reactants and/or by suitably purging one or moreportions of a reactant delivery system shared by incompatible processreactants.

For example, FIG. 34 shows a flow chart illustrating an embodiment of amethod 3400 of transitioning, in-situ, from a first film depositionprocess to a second film deposition process with an intervening purgestep. Method 3400 includes, at 3402, in a first film deposition phase,depositing a first layer of film. At 3404, method 3400 includes purgingone or more portions of a reactant delivery line and/or a processstation shared by a process reactant of the first film deposition phasethat is incompatible with a process reactant of a second film depositionphase. At 3406, method 3400 includes, in the second film depositionphase, depositing a second layer of film on top of the first layer offilm.

FIGS. 35A and 35B show an example flow chart illustrating an embodimentof a method 3500 purging one or more portions of a reactant deliveryline shared by a process reactant of the first film deposition phasethat is incompatible with a process reactant of a second film depositionphase. In the example method depicted in FIGS. 35A and 35B, a processstation is being transitioned from a TEOS-based silicon dioxide filmdeposition process to a silane-based silicon nitride film depositionprocess. Specifically, FIG. 35A shows a first portion of method 3500directed at performing post-deposition purges (“post-purges”) of theTEOS and oxygen delivery lines and at performing a purge of the processstation, while FIG. 35B shows a second portion of method 3500 directedat performing optional pre-deposition purges (“pre-purges”) of thesilane and ammonia delivery lines. It will be appreciated that thisexample is provided merely for illustrative purposes, and that othersuitable purging cycles for other suitable deposition processtransitions may be substituted within the scope of this disclosure.

Referring to FIG. 35A, method 3500 includes, at 3502, stopping the flowof process gases to the process station. Next, method 3500 enters a TEOSdelivery line post-purge phase. At 3504, method 3500 includes purgingthe TEOS delivery line. In some embodiments, an oxygen flow may be usedto purge the TEOS delivery line. For example, oxygen may be supplied ata suitable flow rate to purge delivery lines and hardware downstream ofmixing point where the TEOS delivery line is fluidly connected with theoxygen source.

At 3506, method 3500 includes evacuating the TEOS delivery line. In someembodiments, the TEOS delivery line may be evacuated by evacuating theprocess station. For example, the purge gas in the TEOS delivery linemay be turned off and the process station pressure may be controlled toevacuate a portion of the remaining gas in the process station. In someembodiments, the process station may be controlled to a base pressure bycommanding a process station control valve to a fully open setting. Onenon-limiting example of a process station base pressure is a pressure ofless than 0.5 torr. Additionally or alternatively, in some embodiments,a separate TEOS delivery line evacuation pipe may be used to evacuateresidual gases from the TEOS delivery line.

At 3508, method 3500 includes checking whether additional TEOS deliveryline purging is indicated. For example, in some embodiments, a recipemay indicate a number of TEOS delivery line purge cycles to beperformed. If additional TEOS delivery line purging is indicated, method3500 returns to 3504. In some embodiments, between two and five purgeand evacuation cycles may be performed. In one non-limiting example,each purge and evacuation cycle may have a duration of between 30seconds and 60 seconds.

If additional TEOS delivery line purging is not indicated, method 3500continues to 3510, where method 3500 enters an oxygen delivery linepost-purge phase. At 3510, includes purging the oxygen delivery line. Insome embodiments, nitrogen supplied at a suitable flow rate may be usedto purge the silane delivery line.

At 3512, method 3500 includes evacuating the oxygen delivery line. Insome embodiments, the oxygen delivery line may be evacuated byevacuating the process station. For example, the purge gas in the oxygendelivery line may be turned off and the process station pressure may becontrolled to evacuate a portion of the remaining gas in the processstation. In some embodiments, the process station may be controlled to abase pressure by commanding a process station control valve to a fullyopen setting. One non-limiting example of a process station basepressure is a pressure of less than 0.5 torr. Additionally oralternatively, in some embodiments, a separate oxygen delivery lineevacuation pipe may be used to evacuate residual gases from the oxygendelivery line.

At 3514, method 3500 includes checking whether additional oxygendelivery line purging is indicated. For example, in some embodiments, arecipe may indicate a number of oxygen delivery line purge cycles to beperformed. If additional oxygen delivery line purging is indicated,method 3500 returns to 3510. In some embodiments, between two and fivepurge and evacuation cycles may be performed. In one non-limitingexample, each purge and evacuation cycle may have a duration of between30 seconds and 60 seconds.

If additional oxygen delivery line purging is not indicated, method 3500continues to 3516, where method 3500 enters process station purge phase.At 3516, method 3500 includes purging the process station. In someembodiments, a purge gas is supplied to the process station to sweepsmall particles from plumbing and/or hardware surfaces within theprocess station, the mixing vessel, etc. In one non-limiting example,nitrogen and/or an inert gas is supplied to sweep away small particlesand displace oxygen adsorbed to process station hardware, such as themixing vessel, a showerhead gas distributor, process station walls, etc.

At 3518, method 3500 includes evacuating the process station. In someembodiments, the process station may be pumped down to the base pressureof the process station. Optionally, the oxygen supply manifold may beisolated by closing one or more process valves. This may preventback-diffusion of subsequently delivered gases into the oxygen supplymanifold.

At 3520, method 3500 includes checking whether additional processstation purging is indicated. For example, in some embodiments, a recipemay indicate a number of process station purge cycles to be performed.If additional process station purging is indicated, method 3500 returnsto 3516. In some embodiments, between two and five purge and evacuationcycles may be performed. In one non-limiting example, each purge andevacuation cycle may have a duration of between 5 seconds and 20seconds. In some embodiments, if additional process station purging isnot indicated and if pre-purging the silane delivery line is notindicated, method 3500 continues to 3522, where method 3500 checkswhether an optional pre-purge of one or more of the silane and ammoniadelivery lines may be indicated. If pre-purging is not indicated, method3500 ends. If a pre-purge of the silane delivery line is indicated,method 3500 continues to FIG. 35B.

Turning to FIG. 35B, method 3500 includes, at 3524, purging the silanedelivery line. In some embodiments, a nitrogen flow may be used to purgethe silane delivery line. For example, nitrogen supplied at a suitableflow rate may be used to purge the silane delivery line.

At 3526, method 3500 includes evacuating the silane delivery line. Insome embodiments, the silane delivery line may be evacuated byevacuating the process station. For example, the purge gas in the silanedelivery line may be turned off and the process station pressure may becontrolled to evacuate a portion of the remaining gas in the processstation. In some embodiments, the process station may be controlled to abase pressure as described above. Additionally or alternatively, in someembodiments, a separate silane delivery line evacuation pipe may be usedto evacuate residual gases from the silane delivery line.

At 3528, method 3500 includes checking whether additional silanedelivery line purging is indicated. For example, in some embodiments, arecipe may indicate a number of silane delivery line purge cycles to beperformed. If additional silane delivery line purging is indicated,method 3500 returns to 3524. In some embodiments, between two and fivepurge and evacuation cycles may be performed. In one non-limitingexample, each purge and evacuation cycle may have a duration ofapproximately 60 seconds. Optionally, in some embodiments the silanedelivery line may be isolated by closing one or more process valves.This may prevent back-diffusion of subsequently delivered gases into thesilane delivery line.

In some embodiments, if additional silane delivery line purging is notindicated, method 3500 continues to 3540, where method 3500 checkswhether an optional pre-purge of the ammonia delivery line is beindicated. If pre-purging of the ammonia delivery line is not indicated,method 3500 ends.

If a pre-purge of the ammonia delivery line is indicated, method 3500continues to 3542. At 3542, method 3500 includes purging the ammoniadelivery line. In some embodiments, a nitrogen flow may be used to purgethe ammonia delivery line. For example, nitrogen may be supplied at asuitable flow rate to purge the ammonia delivery line.

At 3544, method 3500 includes evacuating the ammonia delivery line. Insome embodiments, the ammonia delivery line may be evacuated byevacuating the process station. For example, the purge gas in theammonia delivery line may be turned off and the process station pressuremay be controlled to evacuate a portion of the remaining gas in theprocess station. In some embodiments, the process station may becontrolled to a base pressure as described above. Additionally oralternatively, in some embodiments, a separate ammonia delivery lineevacuation pipe may be used to evacuate residual gases from the ammoniadelivery line.

At 3546, method 3500 includes checking whether additional ammoniadelivery line purging is indicated. For example, in some embodiments, arecipe may indicate a number of ammonia delivery line purge cycles to beperformed. If additional ammonia delivery line purging is indicated,method 3500 returns to 3546. In some embodiments, between two and fivepurge and evacuation cycles may be performed. In one non-limitingexample, each purge and evacuation cycle may have a duration ofapproximately 60 seconds. If additional ammonia delivery line purging isnot indicated, method 200 ends. Optionally, in some embodiments theammonia delivery line may be isolated by closing one or more processvalves. This may prevent back-diffusion of subsequently delivered gasesinto the ammonia delivery line.

It will be appreciated that other suitable arrangements of portions ofmethod 3500 are included within the scope of the present disclosure. Forexample, in some embodiments, one or more process station purge cyclesmay be included between the silane delivery line purge and the ammonialine purge. Further, the present disclosure is not limited to asilane/ammonia/TEOS system described in method 3500. Thus, it will beappreciated that other suitable delivery line and process station purgecycles for other incompatible process gases are included within thescope of the present disclosure. Further still, any suitable purge gasmay be used. Other example purge gases include, but are not limited to,helium, argon, etc.

The methods described herein may be performed by any suitable apparatus.A suitable apparatus includes hardware for accomplishing the processoperations and a system controller having instructions for controllingprocess operations in accordance with the present invention. Forexample, in some embodiments, the hardware may include one or moreprocess stations included in a process tool.

The system controller will typically include one or more memory devicesand one or more processors configured to execute instructions forcontrolling process operations so that the apparatus will perform amethod in accordance with the present disclosure. For example, in someembodiments, the system controller may operate various valves,temperature controllers, plasma controllers, and pressure controllers toadjust process conditions within the apparatus. In some embodiments,machine-readable media containing instructions for controlling processoperations in accordance with the present disclosure may be coupled tothe system controller.

For example, FIG. 36 schematically shows an example embodiment of aprocess station 3600. For simplicity, process station 3600 is depictedas a standalone process station having a process chamber body 3672 formaintaining a low-pressure environment. However, it will be appreciatedthat a plurality of process stations 3600 may be included in a commonlow-pressure process tool environment. Process station 3600 includes aprocess gas delivery line 3674 for providing process gases, such asinert gases, precursors, reactants, and treatment reactants, fordelivery to process station 3600. In the example shown in FIG. 36, ashowerhead 3678 is included to distribute process gases within processstation 3600. Substrate 3686 is located beneath showerhead 3678, and isshown resting on a holder 3680 supported by a pedestal 3682. In someembodiments, pedestal 3682 may be configured to rotate about a verticalaxis. Additionally or alternatively, pedestal 3682 may be configured totranslate horizontally and/or vertically.

In some embodiments, showerhead 3678 may be a dual-plenum ormulti-plenum showerhead. For example, FIG. 37 schematically shows anembodiment of a dual-plenum showerhead 3700. A first set of holes 3702receives gas from a first process gas delivery line 3712 and a secondset of holes 3704 receives gas from a second process gas delivery line3714. Such physical isolation of process gases may provide an approachto reducing small particle generation from reaction between incompatibleprocess gases in process gas delivery plumbing upstream of showerhead3700. Any suitable segregation scheme may be employed. For example, inone scenario, holes 3702 may be dedicated to a silicon dioxide filmdeposition process while holes 3704 may be dedicated to a siliconnitride film deposition process. In another scenario, holes 3704 may bededicated to oxidizing reactants while holes 3704 may be dedicated toreducing reactants. While the example shown in FIG. 37 is a dual-plenumshowerhead, it will be appreciated that, in some embodiments, ashowerhead may be a multi-plenum showerhead having three or more sets ofholes.

Showerhead 3678 and holder 3680 electrically communicate with RF powersupply 3688 and matching network 3690 for powering a plasma 3692. Plasma3692 may be contained by a plasma sheath 3694 located adjacent toshowerhead 3678 and holder 3680. While FIG. 36 depicts acapacitively-coupled plasma, plasma 3692 may be generated by anysuitable plasma source. In one non-limiting example, plasma 3692 mayinclude a parallel plate plasma source.

In the embodiment shown in FIG. 36, RF power supply 3688 may provide RFpower of any suitable frequency. In some embodiments, RF power supply3688 may be configured to control high- and low-frequency RF powersources independently of one another. Example low-frequency RF powersmay include, but are not limited to, frequencies between 200 kHz and2000 kHz. Example high-frequency RF powers may include, but are notlimited to, frequencies between 13.56 MHz and 80 MHz. Likewise, RF powersupply 3688 and matching network 3690 may be operated at any suitablepower to form plasma 3692. Examples of suitable powers include, but arenot limited to, powers between 250 W and 5000 W for a high-frequencyplasma and powers between 0 W and 2500 W for a low-frequency plasma fora four-station multi-process tool including four 15-inch showerheads. RFpower supply 3688 may be operated at any suitable duty cycle. Examplesof suitable duty cycles include, but are not limited to, duty cycles ofbetween 5% and 90%.

Returning to FIG. 36, in some embodiments, holder 3680 may betemperature controlled via heater 3684. Further, in some embodiments,pressure control for process station 3600 may be provided by butterflyvalve 3696 or by any other suitable pressure control device. As shown inFIG. 36, butterfly valve 3696 throttles a vacuum provided by a vacuumpump (not shown) fluidly coupled to process station exhaust line 3698.However, in some embodiments, pressure control of process station 3600may also be adjusted by varying a flow rate of one or more gasesintroduced to process station 3600.

It will be appreciated that control of one or more process parametersmay be provided locally (e.g., RF power may be controlled by a plasmacontroller communicating with RF power supply 3688, process stationpressure may be controlled by a valve controller communicating withbutterfly valve 3696 or with gas metering valves or flow controllersincluded coupled with process gas delivery line 3674, etc.) or underpartial or total control provided by a system controller (described inmore detail below) communicating with process station 3600 withoutdeparting from the scope of the present disclosure.

As described above, one or more PECVD process stations may be includedin a multi-station processing tool. In some embodiments of amulti-station process tool, control and/or supply of various processinputs (e.g., process gases, plasma power, heater power, etc.) may bedistributed from shared sources to a plurality of process stationsincluded in the process tool. For example, in some embodiments, a sharedplasma generator may supply plasma power to two or more processstations. In another example, a shared gas distribution manifold maysupply process gases to two or more process stations. Some non-limitingexample embodiments of multi-station processing tools are describedbelow.

FIG. 38 schematically shows an example process tool 3840, which includesa plurality of processing stations 3842 in a low-pressure environment.By maintaining each station in a low-pressure environment, defectscaused by vacuum breaks between film deposition processes may beavoided. In the example shown in FIG. 25, each processing station 3842is configured to deposit TEOS-based silicon dioxide films andsilane-based silicon nitride films. Process gases for each processingstation 3842 are supplied by a common mixing vessel 3844 for blendingand/or conditioning process gases prior to delivery. In someembodiments, mixing vessel 3844 may be temperature controlled. Processgases may be supplied from a plurality of process gas manifolds, each ofwhich may include any suitable process gas. For example, FIG. 38 depictsa manifold A including silane and nitrogen fluidly communicating with asilane delivery line 3845; a manifold B including ammonia and nitrogenfluidly communicating with an ammonia delivery line 3847; and a manifoldC including oxygen, helium, and argon fluidly communicating with a TEOSdelivery line 3848. However, it will be appreciated that other suitablearrangements are included within the scope of the present disclosure. Inone non-limiting example, helium and/or argon are provided to each ofmanifolds A, B, and C.

In the example shown in FIG. 38, TEOS is introduced into TEOS deliveryline 3848 fluidly communicating with manifold C at mixing point 3846. Insome embodiments, liquid TEOS may be vaporized by optional vaporizer3849 upstream of mixing point 3846.

Deposition of each film type may occur by a process that may include oneor more of the above-described phases suitably modified for in-situdeposition of TEOS-based silicon dioxide films and silane-based siliconnitride films. Because each processing station 3842 is configured toprovide each film type, additional purge and/or evacuation steps may beincluded within one or both processes to separate incompatible processgases. For example, in one scenario, residual oxygen adsorbed toplumbing surfaces may react with subsequently introduced silane to formfine silicon dioxide particulates. In another scenario, residual TEOSmay react with subsequently introduced ammonia to form siliconoxynitride particulates. These particulates may be entrained during agas flow event and may be distributed on the substrate surface asparticle defects. One approach to addressing generation of suchparticles is by using one or more purge and/or evacuation cycles todisplace incompatible process gases from surfaces and/or spaces sharedby the process gases during transitions between deposition events.

In some embodiments, separate mixing vessels may be employed, separatingincompatible precursors and potentially reducing purging and/orevacuation times for portions of the process gas delivery plumbing. Forexample, FIG. 39 schematically shows an embodiment example process tool3990, which includes a plurality of processing stations 3992 in alow-pressure environment.

Process gases may be supplied to process tool 3990 from a plurality ofprocess gas manifolds, each of which may include any suitable processgas. For example, FIG. 39 depicts a manifold A including silane andnitrogen fluidly communicating with process tool 3990; a manifold Bincluding ammonia and nitrogen fluidly communicating with process tool3990; and a manifold C including oxygen, helium, and argon fluidlycommunicating with process tool 3990. However, it will be appreciatedthat other suitable arrangements are included within the scope of thepresent disclosure. In one non-limiting example, helium and/or argon areprovided to each of manifolds A, B, and C.

In the example shown in FIG. 39, process stations 3992 are configured todeposit TEOS-based silicon dioxide films and silane-based siliconnitride films. Oxide film reactants, shown in FIG. 39 as TEOS andoxygen, are delivered to each processing station 3992 via an oxidesystem mixing vessel 3994. In the example shown in FIG. 39, liquid TEOSmay be vaporized by optional vaporizer 3999 and mixed with oxygensupplied from manifold C at mixing point 3991.

In some embodiments, oxide system mixing vessel 3994 may be heated todiscourage condensation of TEOS vapor. Additionally or alternatively, insome embodiments, oxide system mixing vessel 3994 may be configured tobe purged and/or evacuated. Such approaches may potentially reduce theformation of small silicon oxide particles within oxide system mixingvessel 3994 and/or other process gas plumbing. While FIG. 39 shows asingle oxide system mixing vessel 3994, it will be appreciated that anysuitable number of oxide system mixing vessels 3994 may be includedwithin the scope of the present disclosure. For example, in someembodiments, two or more oxide system mixing vessels 3994 may beincluded; in some other embodiments, oxide system mixing vessel 3994 maybe omitted. Additionally or alternatively, in some embodiments, anysuitable number or configuration of mixing device, either dynamic orstatic, may be included in oxide system mixing vessel 3994 or fluidlycoupled therewith.

Nitride film reactants, shown in FIG. 39 as silane and ammonia, aresupplied via manifolds A and B, respectively, to each processing station3992 via nitride system mixers 3995. In some embodiments, nitride systemmixers 3995 may include dynamic or static mixing elements. In onenon-limiting example, nitride system mixers 3995 may be static gasmixers including static, helically-shaped baffles. Additionally oralternatively, in some embodiments, nitride system mixers 3995 mayinclude one or more heated mixing vessels. While FIG. 39 shows thatprocess tool 3990 comprises two nitride system mixers 3995 for mixingnitride film reactants, it will be appreciated that any suitable numberof nitride system mixers 3995 may be employed within the scope of thepresent disclosure. In some examples, three or more nitride systemmixers may be used; in some other examples, a single nitride systemmixer 3995 may be used, or the nitride system mixer 3995 may be omitted.In some embodiments, one or more nitride system mixers 3995 may includea mixing vessel. For example, in one scenario, one or more mixingvessels having no baffles may be substituted for one or more nitridesystem mixers 3995.

In some embodiments, inert gases, such as argon, helium, and nitrogen,may be supplied to one or more process stations, providing purging,process gas dilution and/or pressure control capability. In the exampleshown in FIG. 39, argon is provided to each process station 3992 via twoinert mixers 3996. However, it will be appreciated that, in someembodiments, any suitable number of inert mixers 3996 may be employed,or in the alternative, that inert mixers 3996 may be omitted.

A plurality of valves 3998 for each process station 3992 isolateupstream portions of the oxide film gas delivery plumbing from thenitride film gas delivery plumbing from one another and from a processstation feed 3997. This may prevent reactions between incompatiblereactants. In some embodiments, the arrangement of valves 3998 maycomparatively reduce a volume of process station feed 3997, furtherreducing potential reactions between incompatible reactants.

While FIG. 39 depicts three valves 3998 and a single process stationfeed 3997 serving each process station 3992, it will be appreciated thatany suitable number of valves 3998 and process station feeds 3997 may beemployed. For example, in some embodiments, each process gas may have aseparate process station feed 3997 serving each process station 3992.

Further, it will be appreciated that, in some embodiments, two or morevalves 3998 serving a common process station 3992 may be logically tiedtogether via any suitable method (e.g., via electronic or pneumaticapproaches) to act as a virtual single valve. For example, one or moresets of three valves 3998 serving an associated process station 3992 maybe operated by a process station controller (not shown) as a virtualthree-way valve. This may provide a measure of process defect control,preventing concurrent supply of incompatible gases. Alternatively, insome embodiments, any suitable number of valves 3998 may be physicallyunited within a common valve assembly, such as an actual three-wayvalve. While not shown in FIG. 39, it will be appreciated that anysuitable number of additional manually- or programmatically-controlledvalves may be included within the scope of the present disclosure. Suchvalves may provide additional process control capability, leak-checkcapability, etc.

Deposition of each film type may occur by a process that may include oneor more of the above-described phases suitably modified for in-situdeposition of TEOS-based silicon dioxide films and silane-based siliconnitride films. Because each process station 3992 is configured toprovide each film type, additional purge and/or evacuation steps may beincluded within one or both processes to separate incompatible processgases. For example, in one scenario, residual oxygen adsorbed toplumbing surfaces may react with subsequently introduced silane to formfine silicon dioxide particulates. In another scenario, residual TEOSmay react with subsequently introduced ammonia to form siliconoxynitride particulates. These particulates may be entrained during agas flow event and may be distributed on the substrate surface asparticle defects. One approach to addressing generation of suchparticles is by using one or more purge and/or evacuation cycles todisplace incompatible process gases from surfaces and/or spaces sharedby the process gases during transitions between deposition events.

In the example shown in FIG. 39, each processing station 3992 isconfigured to deposit TEOS-based silicon dioxide films and silane-basedsilicon nitride films. However, it will be appreciated that any suitablenumber of process stations 3992 may be “hard” dedicated to depositingeither film via appropriate physical isolation of process gases, or,that any suitable number of process stations 3992 may be “soft”dedicated to depositing either film via process recipe, temporaryphysical isolation of process gases, or software-based isolation ofprocess gases.

For example, in some embodiments, particle generation caused byincompatible process gases may be addressed by segregating TEOS-basedsilicon dioxide deposition process hardware from silane-based siliconnitride deposition process hardware on a common process tool. Forexample, FIG. 40 schematically shows a process tool 4050 having aplurality of silicon nitride process stations 4052 and a plurality ofsilicon oxide process stations 4054. Process tool 4050 includes threegas manifolds. Manifold A is supplied with silane and nitrogen. ManifoldB is supplied with nitrogen, ammonia, nitrogen trifluoride (NF₃), whichmay be used to provide in-situ process station cleaning capability), andnitrous oxide. In the embodiment shown in FIG. 40, manifolds A and B areplumbed to a common mixing vessel 4056. However, in some embodiments,mixing vessel 4056 may be omitted, and manifolds A and B may be plumbeddirectly to each processing station 4052. Manifold C is supplied withargon, helium, nitrogen, and oxygen, which are routed via a deliveryline to mixing vessel 4058. TEOS vapor, which may be generated atoptional vaporizer 4059, is blended with oxygen in a delivery linefluidly communicating with manifold C at mixing point 4057 and routed tomixing vessel 4058.

By segregating the silicon dioxide and the silicon nitride depositionprocesses to independent processing stations having independent processgas delivery systems, purge and/or evacuation times at each processingstation may be reduced, which may reduce an overall cycle time for theprocessing tool. For example, in one process recipe, a film stack ofalternating silicon dioxide and silicon nitride films may be depositedby deposition of a silicon dioxide layer in either of the silicon oxideprocess stations 4054, followed by moving the substrate, such as by asubstrate transfer system, to a silicon nitride process station 4052 fordeposition of a silicon nitride layer. Thus, an alternating film stackmay be built up by an appropriate number of substrate transferoperations between process stations 4052 and 4054.

FIG. 41 schematically shows an example process tool 4160, which includesa plurality of processing stations 4162 in a low-pressure environment.Each processing station 4162 is configured to deposit N₂O and TEOS-basedsilicon dioxide and silane-based silicon nitride. Each processingstation 4162 is supplied by a common mixing vessel 4164 for blendingand/or conditioning process gases prior to delivery to each processingstation 4162.

FIG. 42 shows a schematic view of an embodiment of another multi-stationprocessing tool 4200 with an inbound load lock 4202 and an outbound loadlock 4204. A robot 4206, at atmospheric pressure, is configured to movesubstrates from a cassette loaded through a pod 4208 into inbound loadlock 4202 via an atmospheric port 4210. Inbound load lock 4202 iscoupled to a vacuum source (not shown) so that, when atmospheric port4210 is closed, inbound load lock 4202 may be pumped down. Inbound loadlock 4202 also includes a chamber transport port 4216 interfaced withprocessing chamber 4214. Thus, when chamber transport 4216 is opened,another robot (not shown) may move the substrate from inbound load lock4202 to a pedestal of a first process station for processing.

In some embodiments, inbound load lock 4202 may be connected to a remoteplasma source (not shown) configured to supply a plasma to load lock.This may provide remote plasma treatments to a substrate positioned ininbound load lock 4202. Additionally or alternatively, in someembodiments, inbound load lock 4202 may include a heater (not shown)configured to heat a substrate. This may remove moisture and gasesadsorbed on a substrate positioned in inbound load lock 4202. While theembodiment depicted in FIG. 42 includes load locks, it will beappreciated that, in some embodiments, direct entry of a substrate intoa process station may be provided.

The depicted processing chamber 4214 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 42. In someembodiments, processing chamber 4214 may be configured to maintain a lowpressure environment so that substrates may be transferred among theprocess stations without experiencing a vacuum break and/or airexposure. Each process station depicted in FIG. 42 includes a processstation substrate holder (shown at 4218 for station 1) and process gasdelivery line inlets. In some embodiments, one or more process stationsubstrate holders 4218 may be heated.

In some embodiments, each process station may have different or multiplepurposes. For example, a process station may be switchable between anultra-smooth PECVD process mode and a conventional PECVD or CVD mode.Additionally or alternatively, in some embodiments, processing chamber4214 may include one or more matched pairs of ultra-smooth PECVD andconventional PECVD stations (e.g., a pair including an ultra-smoothPECVD SiO₂ station and a conventional PECVD SiN station). In anotherexample, a process station may be switchable between two or more filmtypes, so that stacks of different film types may be deposited in thesame process chamber.

While the depicted processing chamber 4214 comprises four stations, itwill be understood that a processing chamber according to the presentdisclosure may have any suitable number of stations. For example, insome embodiments, a processing chamber may have five or more stations,while in other embodiments a processing chamber may have three or fewerstations.

FIG. 42 also depicts an embodiment of a substrate handling system 4290for transferring substrates within processing chamber 4214. In someembodiments, substrate handling system 4290 may be configured totransfer substrates between various process stations and/or between aprocess station and a load lock. It will be appreciated that anysuitable substrate handling system may be employed. Non-limitingexamples include substrate carousels and substrate handling robots.

It will be appreciated that, in some embodiments, a low-pressuretransfer chamber may be included in a multi-station processing tool tofacilitate transfer between a plurality of processing chambers. Forexample, FIG. 43 schematically shows another embodiment of amulti-station processing tool 4300. In the embodiment shown in FIG. 43,multi-station processing tool 4300 includes a plurality of processingchambers 4214 including a plurality of process stations (numbered 1through 4). Processing chambers 4214 are interfaced with a low-pressuretransport chamber 4304 including a robot 4306 configured to transportsubstrates between processing chambers 4214 and load lock 4308. Anatmospheric substrate transfer module 4310, including an atmosphericrobot 4312, is configured to facilitate transfer of substrates betweenload lock 4308 and pod 4208.

Turning back to FIG. 42, multi-station processing tool 4200 alsoincludes an embodiment of a system controller 4250 employed to controlprocess conditions and hardware states of processing tool 4200. Forexample, in some embodiments, system controller 4250 may control one ormore process parameters during an ultra-smooth PECVD film depositionphase to control an absolute roughness of the film surface. While notshown in FIG. 43, it will be appreciated that the embodiment ofmulti-station processing tool 4300 may include a suitable systemcontroller like the embodiment of system controller 4250 shown in FIG.42.

System controller 4250 may include one or more memory devices 4256, oneor more mass storage devices 4254, and one or more processors 4252.Processor 4252 may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.

In some embodiments, system controller 4250 controls all of theactivities of processing tool 4200. System controller 4250 executesmachine-readable system control software 4258 stored in mass storagedevice 4254, loaded into memory device 4256, and executed on processor4252. System control software 4258 may include instructions forcontrolling the timing, mixture of gases, chamber and/or stationpressure, chamber and/or station temperature, substrate temperature,target power levels, RF power levels, substrate pedestal, chuck and/orsusceptor position, and other parameters of a particular processperformed by processing tool 4200. System control software 4258 may beconfigured in any suitable way. For example, various process toolcomponent subroutines or control objects may be written to controloperation of the process tool components for performing various processtool processes. System control software 4258 may be coded in anysuitable computer readable programming language.

In some embodiments, system control software 4258 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. For example, each phase of anultra-smooth PECVD process may include one or more instructions forexecution by system controller 4250. The instructions for settingprocess conditions for an ultra-smooth PECVD process phase may beincluded in a corresponding ultra-smooth PECVD recipe phase. In someembodiments, the ultra-smooth PECVD recipe phases may be sequentiallyarranged, so that all instructions for an ultra-smooth PECVD processphase are executed concurrently with that process phase.

Other computer software and/or programs stored on mass storage device4254 and/or memory device 4256 associated with system controller 4250may be employed in some embodiments. Examples of programs or sections ofprograms for this purpose include a substrate positioning program, aprocess gas control program, a pressure control program, a heatercontrol program, and a plasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto process stationsubstrate holder 4218 and to control the spacing between the substrateand other parts of processing tool 4200.

A process gas control program may include code for controlling gascomposition and flow rates and optionally for flowing gas into one ormore process stations prior to deposition in order to stabilize thepressure in the process station. A pressure control program may includecode for controlling the pressure in the process station by regulating,for example, a throttle valve in the exhaust system of the processstation, a gas flow into the process station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations.

In some embodiments, there may be a user interface associated withsystem controller 4250. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 4250 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), pressure, temperature, etc. Theseparameters may be provided to the user in the form of a recipe, whichmay be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 4250 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of processing tool 4200.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 4250 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RF biaspower level, pressure, temperature, etc. The instructions may controlthe parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

The various hardware and method embodiments described above may be usedin conjunction with lithographic patterning tools or processes, forexample, for the fabrication or manufacture of semiconductor devices,displays, LEDs, photovoltaic panels and the like. Typically, though notnecessarily, such tools/processes will be used or conducted together ina common fabrication facility.

Lithographic patterning of a film typically comprises some or all of thefollowing steps, each step enabled with a number of possible tools: (1)application of photoresist on a workpiece, i.e. substrate, using aspin-on or spray-on tool; (2) curing of photoresist using a hot plate orfurnace or other suitable curing tool; (3) exposing the photoresist tovisible or UV or x-ray light with a tool such as a wafer stepper; (4)developing the resist so as to selectively remove resist and therebypattern it using a tool such as a wet bench or a spray developer; (5)transferring the resist pattern into an underlying film or workpiece byusing a dry or plasma-assisted etching tool; and (6) removing the resistusing a tool such as an RF or microwave plasma resist stripper. In someembodiments, an ashable hard mask layer (such as an amorphous carbonlayer) and another suitable hard mask layer (such as an antireflectivelayer) may be deposited prior to applying the photoresist.

It is to be understood that the configurations and/or approachesdescribed herein are exemplary in nature, and that these specificembodiments or examples are not to be considered in a limiting sense,because numerous variations are possible. The specific routines ormethods described herein may represent one or more of any number ofprocessing strategies. As such, various acts illustrated may beperformed in the sequence illustrated, in other sequences, in parallel,or in some cases omitted. Likewise, the order of the above-describedprocesses may be changed.

The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various processes,systems and configurations, and other features, functions, acts, and/orproperties disclosed herein, as well as any and all equivalents thereof.

1. A plasma-enhanced chemical vapor deposition apparatus configured todeposit a plurality of film layers on a substrate without exposing thesubstrate to a vacuum break between film deposition phases, theapparatus comprising: a process station; a reactant feed fluidly coupledto the process station, the reactant feed configured to supply aparticular reactant gas mixture to the process station during aparticular film deposition phase; a plasma source configured to supply aplasma to the process station; and a controller configured to controlthe plasma source to: generate reactant radicals using the particularreactant gas mixture during the particular deposition phase, and sustainthe plasma during a transition from the particular reactant gas mixturesupplied during the particular deposition phase to a different reactantgas mixture supplied during a different deposition phase, wherein thedifferent deposition phase deposits a material having a differentcomposition from the material deposited in the particular filmdeposition phase.
 2. The apparatus of claim 1, wherein the plasma sourceis further configured to sustain the plasma by controlling one or moreof a process station pressure, a reactant gas concentration, an inertgas concentration, a plasma source power, a plasma source frequency, anda plasma power pulse timing.
 3. The apparatus of claim 1, wherein theplasma source is further configured to control the plasma source at aconstant power during the transition.
 4. The apparatus of claim 1,wherein, during the transition, the plasma source is further configuredto vary a low-frequency plasma source power by a proportionally greateramount than a power variation in a high-frequency plasma source power.5. The apparatus of claim 1, further comprising a showerhead, whereinthe reactant feed is one of a plurality of reactant feeds, and whereinthe showerhead includes a plurality of segregated gas plenums, each gasplenum being coupled to a respective reactant feed of the plurality ofreactant feeds so that two or more incompatible process gases aresegregated from one another in the showerhead.
 6. The apparatus of claim1, wherein the process station is one of a plurality of process stationsincluded within the apparatus, each process station fluidly coupled to ashared mixing volume via the reactant feed, the shared mixing volumeconfigured to generate the particular reactant gas mixture from aplurality of reactant gas sources.
 7. The apparatus of claim 9, furthercomprising another process station fluidly coupled to another reactantfeed, wherein the reactant feeds are fluidly isolated from each other,wherein each process station is fluidly coupled to a separate mixingvolume via the respective reactant feeds, each mixing volume fluidlyconnected to one or more reactant gas sources, the one or more reactantgas sources of each mixing volume being separated from one another.
 8. Asystem comprising the apparatus of claim 1 and a stepper tool.